kibosh

For almost two centuries, kibosh has taxed the ingenuity of etymologists. It was prominent enough in lower-class London speech to attract the attention of Charles Dickens, who used it in 1836 in an early sketch, but little else is certain. Claims were once made that it was Yiddish, despite the absence of a plausible Yiddish source. Another hypothesis points to Gaelic caidhp bháis—pronounced similarly to, and meaning, "coif of death"—explained as headgear a judge put on when pronouncing a death sentence, or as a covering pulled over the face of a corpse when a coffin was closed. But evidence for any metaphorical use of this phrase in Irish is lacking, and kibosh is not recorded as spoken in Ireland until decades after Dickens' use.