1660s, from Spanish vainilla "vanilla plant," literally "little pod," diminutive of vaina "sheath," from Latin vagina "sheath" (see vagina). So called from the shape of the pods. European discovery 1521 by Hernando Cortes' soldiers on reconnaissance in southeastern Mexico. Meaning "conventional, of ordinary sexual preferences" is 1970s, from notion of whiteness and the common choice of vanilla ice cream.
vanilla va·nil·la (və-nĭl'ə)
Any of various tropical American vines of the genus Vanilla, especially V. planifolia, cultivated for its long narrow seedpods from which a flavoring agent is obtained.
The seedpod of this plant. Also called vanilla bean.
A flavoring extract prepared from the cured seedpods of this plant or produced synthetically.
[fr the white color and the perhaps unimaginative choice of vanilla ice cream]