Shakuhachi performer and researcher Gunnar Jinmei Linder has put his PhD thesis online: Deconstructing 'Tradition' in Japanese Music: A Study of Shakuhachi, Historical Authenticity and Transmission of Tradition. I'm still reading through it, but something on page 96 caught my eye:

In the Fudoki the xiao is referred to with the Chinese characters 殺古波乏 with the reading "sha - ku - ha - chi" (semantically the characters mean "kill - old - wave - poor"). This is probably the oldest extant reference to the word 'shakuhachi' in Japan.

And here's the footnote sourcing this claim:

Kurihara, Shakuhachi shikō (1918), 1975, 16. I have attempted to locate this in the original text without any success, both in hardcopy and through Internet sources. (風土記). If this reference is true, it implies that the word shakuhachi was not necessarily written with the semantically correct 尺八. This could be an indication of that the word 'shakuhachi' was known, but not necessarily with the commonly accepted Chinese characters. At this time, words were sometimes written using the phonetic value of the characters, disregarding their semantic meaning.

Now, it struck me as very unlikely that the Fudoki would actually include a reference to the shakuhachi, spelling it 殺古波乏. The first reason is pragmatic: if the shakuhachi was in the Fudoki, it would indeed be the oldest use of the word in recorded Japanese, and it would appear in every summary of the history of the shakuhachi. But there are other, linguistic reasons to doubt this. For one thing, there was no palatalized /sya/ syllable in Old Japanese. For another, in OJ the character 古 invariably represents the syllable /kwo/:

多迦比迦流 比能美古
takapikaru / pi no mikwo
"High-Shining / Child of the Sun" (trans. Cranston)

And while we're at it, 尺 is also found in the OJ corpus, with the "correct" meaning (a length of measure) and the reading /saka/:

吾嗟 八尺之嗟
wa-ga nageku / ya-saka no nageki
"the eight-foot sighs / that I sigh" (trans. me)

So, to summarize, it doesn't seem likely that 殺古波乏 represents a genuine Fudoki spelling at all, let alone that the word shakuhachi was known in that form at that time. But it did seem plausible that Kurihara had been taken in by some fake Fudoki material that was still in circulation at the time, so I dug up the reference in his book.

[...] 又和爾雅には尺八の疏註に「洞簫同堅笛也」とし、日本風土記には簫を殺古波乏（しやくはち）と訓じ、年山紀聞には「尺八の笛等々唐山にては洞簫といふよし」と載せあり [...]

[...] furthermore, in the Wa jiga [a late 17th-C. dictionary by Kaibara Yoshifuru 貝原好古 inspired by the Chinese Erya], the notes for the 'Shakuhachi' [entry] say "A flute of the same form as the dongxiao 洞簫"; in the Nihon fudoki, the character 簫 [xiao] is given the reading 殺古波乏 "sha-ku-ha-chi"; and the Nenzan kibun [an early 19th-C. book of essays by Andō Tameakira 安藤為章] includes the text "the shakuhachi flute ... is in China called the 'dongxiao'" [...]

Incidentally, this paragraph theoretically contains all that you need to solve the mystery of 殺古波乏 (it is neither hoax nor error), but I'll confess that it wasn't enough for me.

Now, I didn't find it very likely that Kurihara had read the whole Fudoki himself, looking for references to the instrument that interested him. He doesn't reference a source, but surely he had one; and given the time period, I reasoned, that source was highly likely to have been the Koji ruien 古事類苑, a Meiji leishu 類書 (sort of like an encyclopedia, but with more quotes from the classics). And, sure enough, the Koji ruien's entry for "shakuhachi" includes the 殺古波乏 quote, with a comment:

〔日本風土記　四　响器〕簫　殺古波乏（シヤクハチ）
○按ズル二、簫ヲシヤクハチト訓ズルハ、亦洞簫即チ尺八ナリト云ヘル、謬ヲ襲グ者ナリ

Nihon fudoki, vol. 4, "响器" [sound-making instruments]: 簫 = 殺古波乏 (shakuhachi)
○ Note: Applying the pronunciation shakuhachi to the character 簫 appears to be a repetition of the erroneous assertion that the dongxiao is [the same as] the shakuhachi.

(Incidentally, this quotation is sandwiched between the Wa jiga quotation and the Nenzan kibun quotation, so Kurihara was indeed probably working straight from the Koji ruien. No big deal; that's what it was for.)

But this reference in the Koji ruien packs so much oddness into so few characters. The Fudoki isn't generally divided into numbered volumes; the parts are referred to by the province they cover — the "Izumo fudoki", etc. And there ain't no province called 响器 — in fact, I'd never seen 响 in a Japanese context before.

That's when it hit me: the work I'm thinking of is a collection of fragments referred to collectively as the Fudoki. It isn't called the Nihon fudoki at all, and never has been, or at least not widely. The Koji ruien reference must be to a completely different book!

And indeed, it was. The Nihon fudoki, or Riben fengtuji, is a Chinese book about Japan written in the 16th century by Hou Jigao 侯継高. Waseda has two editions from the Edo period online, but neither of them include an entry for 簫; fortunately, the Kindai Digital Library has a different edition from the Taishō period which does include it:

Mystery solved: the pronunciation 殺古波乏 is indeed given for the character 簫 in a book called 日本風土記 — but that book is the 16th-century Chinese book by Hou Jigao (and, furthermore, the 殺古波乏 bit may be a much later addition), not the well-known Fudoki from the Nara period, and so it isn't a particularly exciting citation.

Bryan Lowe, Chris Mayo, and a bunch of other advisors and contributors have launched an online Guide to Shōsōin Research, hosted by Vanderbilt University:

What are Shōsōin documents?

Shōsōin 正倉院 is the name of an eighth-century storehouse located on the grounds of the temple Tōdai-ji 東大寺. While it is most famous for its collection of treasures, including many objects that reached Japan via the silk road, it also preserves over 10,000 hand-written documents all dating from the Nara period (710–784). [...]

Why haven't I heard more about these sources?

English-language scholarship has barely scratched the surface of this rich source base. The primary reason for this neglect stems from the complexity of the collection, which has rendered it nearly impossible to use without specialized training. The manuscripts were cut apart and reassembled multiple times both in the eighth century and in the modern era. Publication further complicated matters, as the documents were again rearranged for the compilation of the Dai Nihon komonjo 大日本古文書 series.

There's also a blog and a glossary, both chiefly focused (at present) on how scholars deal with this cut-up mess of invaluable documentation: "The primary task of Shōsōin scholars in Japan is to figure out how these numerous fragments were once related to one another."

Lowe, Mayo, and the other contributs deserve a lot of credit for their work here. I didn't know diddly squat about Shōsōin documents before reading this page, but I do know how tough it can be to find the first foothold in a field like this — that one obscure reference book, tucked away only in a few major libraries, that lets you start exploring a topic in detail rather than in a popularized (or summarized-for-specialists-in-other-fields) form.

I suppose most people reading this also ready Language Log and are therefore aware that word aversion is the hip new topic these days. How timely then that a new cosmetics line recently launched in Japan is called "Moist, Diane."

Well, they also use other punctuatings, like "Moist-Diane" and "Moist Diane," but I don't suppose those are any better from the point of view of the moist-averse. Who, incidentally, should also appreciate the tag line: "For the moisture of all women. Moisturized skin. Moisturized hair. Moisturized body."

In conclusion, moist.

Here's another one from Nihon ongaku no nagare (previously on No-sword). This one is from Nihon ongaku no rizumu (日本音楽のリズム, "The rhythm of Japanese music"), by Koizumi Fumio 小泉文夫, and I offer it more as an example of applied Nihonjinron than a theory I take seriously.

Japan's year is divided into four seasons, like Europe's. In south and southeast Asia, some areas have only a rainy season and a dry season, while in others dramatic changes in humidity divide the year into six seasons, punctuated by monsoons. Compared to areas like that, Japan is rich in seasonal change without widely separated extremes in temperature, and this climate must surely be the most important foundation stone on which the Japanese way of life and artistic expression rest.

The work of farming is in preparing the soil, planting the seeds, nurturing the shoots, pulling the weeds, and finally harvesting the crop. The unity of this rhythm cannot be broken down. In music, too, there is the jo 序 or oki 置, then the richly evolving ha 破 or nakaba 中端, and finally the lively kyū 急 or kiri 切. This sense of unity has become the most natural form for expressing things.

The jargon in that paragraph refers to the famous concept of jo-ha-kyū and similar ideas in kabuki/nagauta music.

This would seem to be common to all peoples (minzoku), but such is not necessarily the case. For example, among hunting peoples and peoples built on the foundations of a hunting culture, short, repeated phrases and forms in which it is unclear when the work began or when it will end are common. Indeed, the work of hunting means leaping into action the moment that prey appears, but when prey will appear cannot be planned in advance. The day-to-day life is on a completely different rhythmic base from that of farmers, who know that a planted seed will certainly sprout but will not bear fruit until august, no matter how much of a rush the farmer may be in.

In the music of India and Europe, phrasal repetition is recognized, along with a large-scale structural sense, as a fundamental principle. In Japanese music, on the other hand, the principle of repetition is weak. To put it another way, within European and Indian culture, vegetable rhythms directed towards a beauty of structured form are blended with animal rhythms that reflect the moment-by-moment situation, but in Japanese music the vegetable rhythms seem to be prioritized.

Koizumi also seems quite convinced that traditional Iranian music has a very similar sensibility, but I don't know enough about that to comment.

From Kikkawa Eishi 吉川英史's "Katarimono" ni tsuite (＜語りもの＞について, "About 'katarimono'"), in Nihon ongaku no nagare (日本音楽の流れ, "The flow of Japanese music"), ed. Yamagawa Naoharu 山川直治), translation mine:

When "talking" (kataru), performers communicate events and circumstances in a way that the listener can understand. Their words, therefore, must be understood clearly. As a result, prolonging or freely raising and lowering the pitch of the sounds in the words tends to be avoided. If a performer does want to prolong a sound, they will prolong one that does not carry much meaning. For example, the last sound in a phrase, or particles or verb endings. [...]

The aim of "singing" (utau), on the other hand, is to express emotions, not events and circumstances. There need not necessarily be a listener, and it does not matter of the lyrics are not understood. As a result, words can be freely prolonged, advanced vocal techniques used to raise and lower their pitch, and rhythm of the words can be refashioned into a musical rhythm. This is why even though mikagura, saibara, and folk oiwake are sung in Japanese, they are completely incomprehensible, and sound like long vowel practice: "Aaaa, iiii, eeee."

It's been two weeks! Here's a quick translation of a poem called Gaitō 街頭 ("Street"), by Susukida Kyūkin 薄田泣菫. I like this for its almost sestina-ish cycling imagery, its unusual (for Kyūkin) device of ellipsis, and of course because it features a kokyū. The original is basically in 5/7 meter, but I haven't made any attempt to reproduce that here.

A thoroughfare — the sun wells up with tears...
At the beggar-child's kokyū, its scraping,
Sobbing sound... from somewhere,
The faint scent of roasted chestnuts...

Coming and going, the people turn and —
"Ha!" — laugh... the kokyū's lament...
A cloud of dust swirls suddenly,
Flames roll off the chestnuts as they sweat.

The charred nuts, thickly smoking,
Burst open... ah, this hunger!
The chestnut-peddler sneezes,
Her face twisting... the kokyū's weakening...

Coins fall — ah, the kokyū player
Smiles, and proudly
Fills his mouth with chestnut, and he speaks,
A sense of straining at his temples...
The chestnut girl is deaf.

That "beggar-child" is in the original 乞食児, with the furigana かたゐこ. Kata(w)i or kattai is an old Japanese word for "beggar", so old that it has a range of related meanings, like "traveling musician" and even "leper", all deriving from the basic meaning of being poor and reliant on the charity of others.