Cuckold historically referred to a husband with an adulterous wife and is still often used with this meaning. In evolutionary biology, the term cuckold is also applied to males who are unwittingly investing parental effort in offspring that are not genetically their own. Since the 1990s, the term has also been widely used to refer to a sexual fetish in which the fetishist is stimulated by their committed partner choosing to have sex with someone else.
Cuckold derives from the cuckoo bird, alluding to the alleged habit of the female in changing its mate frequently and authentic (in some species) practice of laying its eggs in other nests within its community. The association is common in medieval folklore, literature, and iconography. The original Old English was "kukewold". It was borrowed from Old French "cuccault", which was made up of "cuccu" (old French for the cuckoo bird itself) plus the pejorative suffix – "ault", indicating the named person was being taken advantage of as by a cuckoo bird.
English usage first appears about 1250 in the satirical and polemical poem "The Owl and the Nightingale" (l. 1544). The term was clearly regarded as embarrassingly direct, as evident in John Lydgate's "Fall of Princes" (ca. 1440). In the late 14th century, the term also appeared in Geoffrey Chaucer's Miller's Tale. Shakespeare's poetry often referenced cuckolds, with several of his characters suspected they had become one.