The word "Shojo," that is. Here in the States, we just started to hear about "Shojo" in the context of Shojo Manga (via Shojo Beat) only a few years ago, but apparently the word "Shojo" is almost extinct in Japan itself. Matt Thorn did the scholarship here:
The word itself has been used in Japan for centuries, but it didn’t really become “popular,” it seems, until the turn of the century, which is to say the latter Meiji Period. You can read more about the word on the Wikipedia article I’ve been helping to edit. But since the 1950s, the use of the word in colloquial Japanese had declined to the point where now it is used basically as an adjective for a genre of manga and fiction, and also as a “news/legal” word that is rarely used in daily conversation.
... But what really came as a shock to me was the realization that, unless I’m overlooking something, the word “shôjo” now appears in the title of just one girls’ magazine, Shôjo Comic. There are two other extant girls’ magazines (Bessatsu Friend and BetsuComi) that used to include the word “shôjo” in the title, but the one dropped “shôjo” in 1984, and the other dropped it in 2002.
... The “shôjo” peak is in the late 1910s and the 1920s.... Throughout the 1950s, the word “shôjo” seems to have lost the potency it once enjoyed, and was now being used simply to identify a magazine as being for girls. Publishers began to try to distinguish new magazines from the pack, while at the same time identifying them as “feminine,” by choosing titles such as Margaret (from the French “marguerite”, which is what the Japanese call a daisy). By the 1970s, publishers pretty much stopped including the word in the titles of new girls’ magazines. Now it seems all but extinct.