For some time now, some of my on-line friends have advised me to provide a version of CassidySlangScam without the invective aimed at Cassidy and his supporters. In response to that advice, I am working on providing a glossary of the terms in Cassidy’s ludicrous book How The Irish Invented Slang with a short, simple and business-like explanation of why Cassidy’s version is wrong.
Daniel Cassidy, in his work of fake etymologies, states that the English verb ‘to keen’ comes from the Irish word caoineadh, which means to cry, to mourn or to lament. This is entirely correct. However, the Irish origin of keen is given in all the English dictionaries and long predates Cassidy. You can find more information here: https://www.etymonline.com/word/keen
In fact, Cassidy claimed that there are hundreds of words of Irish origin in American slang which bigoted etymologists had refused to recognise. Examples like this show that where words genuinely derive from Irish, etymologists are more than willing to admit the fact.