cuckoo [ME] The cuckoo is one of those birds whose name echoes the sound of its distinctive call—other examples are curlew [ME], hoopoe [LME], kittiwake [E17th], and peewit [E16th]. You can describe an unwelcome intruder in a place or situation as a cuckoo in the nest [E17th]. This comes from the cuckoo’s habit of laying her eggs to be raised in another bird’s nest. Cuckold [OE], referring to the husband of an unfaithful wife, also derives from cuckoo, and plays on the same cuckoo-in-the-nest idea, although it is not actually the husband who is being the ‘cuckoo’. The reason that a silly or mad person is described as cuckoo [E20th], or is said to have gone cuckoo, is probably that the bird’s monotonously repeated call suggests simple-mindedness. Kook, ‘an eccentric person’, is short for cuckoo. It was first recorded in the 1920s but only really became common in the late 1950s. See also cloud, coccyx.