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.
The word jack as a slang term for money first appears in the US in the 1890s. There is no agreement about its etymology. Some sources note that jack was used as a term for a small coin in English as early as the 16th century. However, the fact that the term jackpot makes its appearance around the 1880s and derives from poker leaves open the possibility that jack is a back formation from jackpot (which really derives from the card jack – the jackpot was won with two jacks). Wherever jack comes from, there is no reason to believe that it derives from Irish.
Daniel Cassidy, in his etymological hoax, How The Irish Invented Slang, claimed that jack derives from the Irish word tiach, which Cassidy defines as: ‘a small purse, a wallet, a budget; fig. money’. Tiach is an archaic word for a bag or satchel and is pronounced chee-ah or tee-ah (not j’aċ, as Cassidy claims). It sounds nothing like jack and it doesn’t mean money. This claim is entirely false.