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 rightly says that this is probably a word of traveller origin. It derives from a word in the Gammon or Shelta language, a kind of disguised backslang based on Irish or Scottish Gaelic used by Irish and Scottish travellers. This is accepted by linguists and did not originate with Cassidy.
Mawley means a hand, and is regarded as a transposed (and de-lenited) version of lámh, which means hand in Irish. Cassidy states that this is really from maille, which he claims means tool in Irish. This is nonsense. There is no such word as maille meaning tool and Cassidy gives no evidence and no source for his claim.