French VAGIN

[Larry Trask]

I'm posting this query for a colleague who doesn't have e-mail.  If
you can help, please reply directly to me.
 
Latin VAGINA `sheath' is grammatically feminine, and so, in general,
are its Romance descendants, including popular French GAINE `sheath'.
But the French learned borrowing, VAGIN `vagina', is unexpectedly
masculine.  Anybody know why?
 
Larry Trask
COGS
University of Sussex
Brighton BN1 9QH
England
 
larryt at cogs.susx.ac.uk