The story you may have heardKibosh is often said to be Yiddish or Hebrew, from a word for 'eighteen' (ḥai) plus a coin, or from kāḇaš 'to subdue'. No such Yiddish word has ever been found, and Merriam-Webster calls the origin obscure. Rival theories include Irish caidhp bháis 'cap of death' (unsupported by evidence), heraldic 'caboshed' and a clogmaker's iron bar. Turkish/Arabic kurbash 'whip' (Cohen, Goranson and Little, 2018) is the best-argued, but it is still contested.