vanilla (n.) Look up vanilla at Dictionary.com
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.