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 Big Onion is a term of recent coinage based on the name for New York, The Big Apple. The Big Onion is used of the ethnic history of the Lower East Side, because that history is like peeling back the layers of an onion. There is a Big Onion walking tour (mentioned by Cassidy) that deals with this ethnic history.
In other words, the term ‘The Big Onion’ is recent and entirely self-explanatory in English.
Cassidy claims that this comes from ‘the big Anonn’, which he claims means ‘far side, other side’. In fact, anonn is a word used only with movement. You can say you went anonn over a river, but when you are on the other side, you are thall, not anonn.