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 came up with false etymologies for a variety of names of New York gangs from the 19th century. One of these false etymologies was the Shirt Tails, which Cassidy claims came from siortálaí, which is a variant form of a word siortaitheoir meaning rummager or ransacker. The received wisdom is that this gang wore their shirt tails outside their trousers so that they could be recognised. This was also the case with factions in Ireland, where the gangs adopted common items of clothing or ways of wearing clothing like an old waistcoat (Seanaveist) or a necktie (Carbhat). These sartorial touches became the equivalent of the blue and red colours of Crips and Bloods, so the English shirt-tail explanation makes a lot of sense.