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.
Most dictionaries regard yack and yacking as versions of the phrase yackety-yack. In other words, they are an onomatopoeic rendering of the noise a set of teeth make when they are chattering.
In Daniel Cassidy’s etymological hoax, How The Irish Invented Slang, Cassidy suggests that it comes from the Irish éagcaoin (properly éagaoin), which is pronounced aygeen and means ‘mourning’ or ‘lamenting’. This is really not similar at all, either in sound or meaning and of course, there is no evidence of yacking having an Irish origin.