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.
In English prisons at the very end of the 17th century (first recorded 1699) and throughout the 18th century, the prisoners used to pay money to the jailers on arrival in return for better treatment. This money was called garnish. The word garnish was already used in mainstream English (first recorded in 1670) by this time for a little extra something added, a ‘bit on the side’, so the use of garnish as a sweetener for a jailer is easy to understand. There is no mystery here, nothing to be explained.
The late Daniel Cassidy tried to explain it in his book of false etymology, How The Irish Invented Slang. As usual, his attempt was totally incompetent. He claimed that garnish (in the sense of sweetener) came from the Irish garanna ar ais, favours back. In theory, this could be an Irish phrase. The word garanna does mean favours and ar ais does mean back.
The problem is that there is no evidence that anyone has ever actually said gar(anna) ar ais in an Irish conversation. Try looking up the phrase on Google. I found two references to this blog. Nothing else.
Then try putting in some of the real phrases used to describe paying back or making restitution in Irish: cúiteamh a dhéanamh le, an comhar a dhíol le. Or what about the word for a tip or gratuity, síneadh láimhe or séisín? These produce a handful of results from different sources because they are real Irish, while Cassidy’s phrase is completely fictional.