Here's an interesting tale of word creation.

It begins with kaminaga 髪長, literally "long-hair". This word was invented sometime in the first millennium C.E. as a substitute for words meaning "monk", which were taboo at certain times and places (the new year, Saikū, Ise Jingū, etc.). It was invented early enough to undergo sound change and be attested later as kōnaga as well, but this did not become the standard, presumably because its morphology was so transparent and easily reconstructible from kami "hair" and naga "long", the former of which did not become kō as an independent word.

Of course, another word was needed for female monastics, and this led to the creation of omina-kaminaga "woman-longhair" and me-kaminaga, "she-longhair". This is attested in a quotation from the 10th-century Engishiki that the Nihon Kokugo Daijiten somewhat disturbingly uses as a cite for both of these two variants:

凡忌詞。内七言。仏称中子。経称染紙。塔称阿良良岐。寺称瓦葺。僧称髪長、尼称女髪長、斎称片膳

There are seven euphemisms [in this category]. Buddha is called "guy in the middle" [of the temple, I guess] (中子) . Sutras are called "dyed paper" (染紙). Stupas are called "wild onions" [or some kind of plant] (阿良良岐). Temples are called "tile-roofs" (瓦葺). Monks are called "longhairs", and nuns are called "woman-longhairs". Food [eaten in accordance with monastic regulations] is called "half-servings" [because monks weren't supposed to eat after noon] (片膳).

So far, so good: an ironic euphemism for the practitioners of a foreign religion. But kaminaga is a simple combination of common morphemes, so of course the word was going to get reinvented. As it turns out, by the Edo period it had been reinvented twice, with the meanings "woman" and "layman" — as opposed to monk. Eventually it began to be used just to refer to long hair and the long-haired in general.

So by the early 20th century, the word kaminaga could be used either as an ironic reference to baldness or a non-ironic reference to having hair. In the latter case, it could refer to anyone, male or female, who had long hair, short hair, or even no hair at all provided that they were not prohibited by their religion from growing it.