Sometimes it's best to leave things alone. You may remember I returned to the word humbug last February after first addressing it before Christmas. Then I said it originated in 18th-century student slang, meaning "a trick, jest, hoax, or deception". I was challenged by a regular interrogator, who said humbug came from the Irish uaim bog, meaning soft copper, a cheap currency dumped on Ireland by would-be English betters.
This coinage was so poor in copper that it and humbug, the word describing it, came to mean something stupid or useless. Said interrogator pointed out, too, that the word kibosh came from caip bháis, meaning "cap of death", a reference to the black cap worn by a judge as he pronounced the death sentence.
"Not so," said Prof David Stifter, of Maynooth University's School of Celtic Studies, explaining that "I have to disagree with some of the etymologies proposed. As a quick glance in any Irish dictionary (Dinneen, Ó Dónaill, the Royal Irish Academy's Dictionary of the Irish Language) would have shown, there is no Irish word uaim meaning copper. What was probably intended is umha (Old Irish umae), 'copper, bronze', but neither does this lend itself phonetically to be borrowed into English as 'hum', nor do the historical dictionaries record examples of umha bog (umae boc) being used as a currency."
He wasn't finished. He went on to put the kibosh on, well, kibosh too. "The word caip for a covering of the head is marginally found in Corpas na Gaeilge 1600-1882, but it seems to be so rare that none of the currently existing dictionaries finds it necessary to record it. The common form is caipín.
"The word caidhp (coif), mentioned by Dinneen, seems to be more to the point, but again it is not of very frequent occurrence. So the two words that could have arguably served as a starting point for this loan do not seem to have had a prominent place in the original language, although it is at least conceivable that an expression like caidhp bháis existed (direct evidence from a text would be welcome, though). Although I cannot say anything definite about 'kibosh', the shape of the word rather suggests a Hebrew origin to me, perhaps via Yiddish."
Who am I to disagree?
Further details of Dr Stifter’s work can be found at http://www.irishtimes.com/culture/treibh/groundbreaking-research-to-establish-chronology-of-medieval-irish-literature-1.2136957