In Daniel Cassidy’s worthless book of fake etymology, he claimed that the word kibosh or kybosh is of Irish origin. Cassidy was certainly not the first to claim this and his sole authority for saying it was a website called Cork Slang Online. The usual claim in relation to its supposed Irish origin is that it comes from caidhp bháis or caidhp an bháis or caip bháis, meaning a cap or cape of death. Some sources also mention cie báis, but cie is not a possible word in Irish orthography.

While caidhp bháis is given as the name of a fungus in Irish dictionaries (the death cap), there is no evidence that this is an ancient expression and it may have been composed on the pattern of the English phrase death cap in the 20^th century.

There are various explanations for the meaning of caidhp bháis as…

Daniel Cassidy did no original research at all. His idea of research was to abstract information from dictionaries, then sneer at the people who had done the work for him. His main targets were the Oxford English Dictionary and Merriam-Webster, who he misrepresented as a clique of WASP bigots. Cassidy called these bastions of the linguistic establishment ‘the dictionary dudes’. In reality, of course, there is more of an implied criticism of the main dictionary-makers in the Irish language in Cassidy’s work, as none of Cassidy’s insane phrases like pá lae sámh and béal ónna are mentioned in any of the Irish dictionaries. It is also interesting that when Cassidy was confronted with a real Irish person who knew some Irish and could clearly see that Cassidy knew nothing about the subject, Cassidy was quite happy to hide behind the authority of the OED. This happened in an RTÉ radio…