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.
Mucker is an English slang term for a person who works with muck or dirt. In parts of America, because the Irish often did the dirtiest jobs, it is used of Irish people. In England and Scotland and Ireland, it often means a friend.
Cassidy claims that this comes from the Irish word mucaire, which means a swineherd. There is no reason to believe this claim, as the word muck is of ancient origin in England and originally derives from a Norse word meaning dung. Muck is unrelated to the Irish word muc, meaning pig. The similarity is pure coincidence. And, of course, people who muck around together are friends, so the use of mucker for a pal is quite natural and easy to understand.
Another myth, which is not mentioned by Cassidy, is that mucker comes from the Irish mo chara, meaning ‘my friend’. Mucker is not found in Ireland first, mo chara does not sound like mucker and the claim that it is of Irish origin is very recent, making its appearance less than twenty years ago.