1200-50;Middle Englishcukeweld, later cok(k)ewold, cukwold < Anglo-French*cucuald (compare Middle Frenchcucuault), equivalent to Old Frenchcocucuckoo + -ald,-alt pejorative suffix (see ribald); apparently orig. applied to an adulterer, in allusion to the cuckoo's habit of laying its eggs in other birds' nests
mid-13c., from O.Fr. cucuault, from cucu (see cuckoo) + pejorative suffix. So called from the female bird's alleged habit of changing mates, or her authentic habit of leaving eggs in another bird's nest. The verb is 1580s, from the noun. Related: Cuckoldry (1520s).