A cuckold is the husband of an adulterous wife; the wife of an adulterous husband is a cuckquean. In biology, a cuckold is a male who unwittingly invests parental effort in juveniles who are not genetically his offspring. A husband who is aware of and tolerates his wife's infidelity is sometimes called a wittol or wittold.
The word cuckold derives from the cuckoo bird, alluding to its habit of laying its eggs in other birds' nests. The association is common in medieval folklore, literature, and iconography.
English usage first appears about 1250 in the medieval debate poem The Owl and the Nightingale. It was characterized as an overtly blunt term in John Lydgate's The Fall of Princes, 1440. Shakespeare's writing often referred to cuckolds, with several of his characters suspecting they had become one.
The word often implies that the husband is deceived; that he is unaware of his wife's unfaithfulness and may not know until the arrival or growth of a child plainly not his (as with cuckoo birds).
The female equivalent cuckquean first appears in English literature in 1562, adding a female suffix to the cuck.
A related word, first appearing in 1520, is wittol, which substitutes wit (in the sense of knowing) for the first part of the word, referring to a man aware of and reconciled to his wife's infidelity.
An abbreviation of cuckold, the term cuck has been used by the alt-right to attack the masculinity of an opponent. It was originally aimed at other conservatives.
In Western traditions, cuckolds have sometimes been described as "wearing the horns of a cuckold" or just "wearing the horns". This is an allusion to the mating habits of stags, who forfeit their mates when they are defeated by another male.
In Italy (especially in Southern Italy, where it is a major personal offence), the insult "cornuto" is often accompanied by the sign of the horns. In French, the term is "porter des cornes". In German, the term is "jemandem Hörner aufsetzen", or "Hörner tragen", the husband is "der gehörnte Ehemann".