Cock a snook/snoot

To cock a snook at someone or something means to express contempt or derision is generally attested in Britain from the late 19th century. It derives from thumbing one’s nose at someone by placing the thumb on the nose and fanning the fingers – what the Americans call ‘the five-fingered salute’. The ‘cock’ part is easily explained meaning to stand out stiffly and erect in defiance, as a cockerel does when crowing. The ‘snook’ part is more difficult to explain because the word only appears in English in this one expression. A plausible notion is that it stems from snout but there is no etymological evidence to back this, although snoot is slang for nose from the late 19th century and the expression is sometimes encountered in the form of cock a snoot at. See also Thumb one’s nose at.