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 claims that the English word clack comes from the Irish clagadh, meaning clatter or rattle. This is not the case, as English clack comes from Middle English clacken, clakken, claken, from Old English *clacian (“to slap, clap, clack”), so there is no room for borrowing from Irish. Irish words like clagadh and clagarnach are thought to derive from clog, the Irish for a bell, but it is not impossible that some Old Norse cognate of clack played a part as well.