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.
Cassidy claimed that the word gaff meaning a boat-hook comes from the Irish gaf or geaf. However, gaf or geaf really comes from English and English got the word from Provencal gaf via French. The word gaffe meaning a blunder is the same word. A quick search on the free and fully-searchable Electronic Dictionary of the Irish Language will confirm that gaf/geaf is not an ancient word in Irish. It is plainly, obviously and clearly a loanword.
Incidentally, the unrelated word gaff meaning a home or a place is from Romani gav.