Is it ensure, insure, or assure?
mid-14c., "of the female sex," from Old French femenin (12c.) "feminine, female; with feminine qualities, effeminate," from Latin femininus "feminine" (in the grammatical sense at first), from femina "woman, female," literally "she who suckles," from root of felare "to suck, suckle" (see fecund). Sense of "woman-like, proper to or characteristic of women" is recorded from mid-15c.
The interplay of meanings now represented in female, feminine, and effeminate, and the attempt to make them clear and separate, has led to many coinages: feminitude (1878); feminile "feminine" (1640s); feminility "womanliness" (1838); femality (17c., "effeminacy;" 1754 "female nature"). Also feminality (1640s, "quality or state of being female"), from rare adjective feminal (late 14c.), from Old French feminal. And femineity "quality or state of being feminine," from Latin femineus "of a woman, pertaining to a woman."