The word 'vagina' was directly borrowed into English in the late 17th century from the identical Latin term, where it meant "sheath, scabbard." This Latin meaning is a metaphorical extension from the Proto-Indo-European root wag- meaning "to cover, protect, enclose." The anatomical application, likening the organ to a sheath for a sword, is a classical Latin usage found in the writings of authors like Aulus Cornelius Celsus. This specific, technical sense was revived in modern scientific Latin and subsequently adopted into English medical terminology, where it has since become the standard formal term.

The word is a simplex loanword from Latin. It is not productively segmented into meaningful substrings in modern English spelling.