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 muck is a term from poker. The muck is used to refer to the discarded cards that are no longer in play and if someone mucks their cards, they fold.
There is nothing mysterious or hard to understand about the etymology of this term. Muck is an ancient English term for dirt, derived from a Scandinavian word for dung, so when cards are out of play and no longer worth anything, they become the muck.
Cassidy implausibly (and unnecessarily) claims that it derives from the Irish word múch, which means to extinguish or smother. This is pronounced mookh (with the kh like the ch of Irish or Scottish loch), so it really sounds nothing like muck.