Etymology

vagina (n.)

"sexual passage of the female from the vulva to the uterus," 1680s, medical Latin, from specialized use of Latin vagina "sheath, scabbard, covering; sheath of an ear of grain, hull, husk" (plural vaginae), a word of uncertain origin. Perhaps cognate with Lithuanian vožiu, vožti  "to cover with a hollow thing," but de Vaan points out that "Obviously, this is a gratuitous proposal." A modern medical word; the Latin word was not used in an anatomical sense in classical times. Anthropological vagina dentata is attested from 1902.

Origin and meaning of vagina
Definitions of vagina

vagina (n.)
the lower part of the female reproductive tract; a moist canal in female mammals extending from the labia minora to the uterus;
the vagina receives the penis during coitus
the vagina is elastic enough to allow the passage of a fetus
From wordnet.princeton.edu