"Ostler, Nicholas. Ad Infinitum: A Biography of Latin and the World It Created. London: HarperPress, 2009. pp. 323-325" says it is from Etruscan.
Please do not sysop delete my comment ;). Zezen (talk) 15:54, 2 April 2016 (UTC)
I saw some discussion on Twitter about the possibility that The Vagina Monologues originated or popularized that sense, so I looked into it. Martha Kirkpatrick, Women’s Sexual Development: Explorations of Inner Space (2012, →ISBN), has an example from 1969, when a psychiatrist character played by a real psychiatrist uses it this way in the film Bob & Carol & Ted & Alice, and another from 1970; I suspect it's even older. - -sche (discuss) 02:47, 11 March 2019 (UTC)
This doesn't seem to be a correct analogy to me, is it? I may be mistaken, but I'd say that in most people's understanding the lips are the front boundary of the mouth, but they are part of it (like a fence that is the boundary of a plot of land, but is included in it). So if that's indeed the general understanding, "mouth" meaning lips is a totum pro parte. Vagina for vulva is something different, because the vagina in biological understanding does not include the vulva. User:2.201.0.62 (discuss) 19:09, 22 March 2019
Is cognation possible with these?