So Leah Dizon just got married (English; Marxy@NJ) to a stylist named Bun. One widely-reported exchange from the press conference:

Asked what made him fall for her, Dizon answered loudly and somewhat cryptically in two English words: "Big peach."

"It is a little bit, sort of, difficult to explain," she said when she was pressed for the meaning of the phrase.

The Japanese press is uniformly reporting this in katakana ("私のビッグ・ピーチ"), usually appending the gloss 桃尻 ("Peach-ass"), God bless 'em.

This takes me back to reading the Tsurezuregusa, which also contains the word 桃尻:

御隨身秦重躬、北面の下野入道信願を、「落馬の相ある人なり、よく／＼つゝしみ給へ」といひけるを、いと眞しからず思ひけるに、信願馬より落ちて死ににけり。道に長じぬる一言、神のごとしと人思へり。さて、「いかなる相ぞ」と人の問ひければ、「きはめて桃尻にして、沛艾の馬を好みしかば、此の相をおほせ侍りき。いつかは申し誤りたる」とぞ云ひける。

When the attendant (zuijin) HADA no Shigemi said to the venerable (nyūdō) SHIMOTSUKE no Shingan of the Imperial Guard, "You have the look of one who would fall from a horse; be very careful," it was taken as nonsense, but then Shingan fell from a horse and died. This superb prediction was thought a very miracle. "What kind of look was it?" one person asked Shigemi. "He had an incredible peach-ass, but he loved spirited horses," came Shigemi's reply. "This was the 'look' I considered. At which point did I err?"

It turns out that momojiri is an old word meaning "bad at horse-riding, unable to sit firmly in the saddle". The metaphor here is not "two shapely rounded halves, like a peach", but rather, "unstable when placed on a flat surface, like a peach". But I'm sure you can imagine how that passage read to me originally.

The word makes another appearance later in the 'Sa:

ある者、子を法師になして、「學問して因果の理をも知り、説經などして世渡るたづきともせよ」といひければ、教のまゝに、説經師にならん爲に、まづ馬に乘り習ひけり。輿・車もたぬ身の、導師に請ぜられん時、馬など迎へにおこせたらんに、桃尻にて落ちなんは、心憂かるべしと思ひけり。

A man made his son enter the priesthood, saying to him, "Study, learn the laws of cause and effect (inga), earn your living by reading sutras and such." The son resolved to do as he was told, and the first step he took towards becoming a priest was learning how to ride a horse. His reasoning was that as a priest with neither palanquin nor carriage, a horse or other animal might be sent to convey him to some function; and that it would be a miserable thing indeed to fall off, peach-assed, while riding.

(Note: This is the beginning of a longer tale with the moral "Don't procrastinate". Kenkō is not actually advocating equestrian training for all novice priests.)