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.
Biddy was originally an expression for an old woman and was also used later in America as a slang term for an Irish maid. Both these terms derive from the English Biddy (or Irish Bidí), which were familiar forms of the common name Bridget. (See the excellent Etymonline: https://www.etymonline.com/word/biddy#etymonline_v_11127.) It is best known in phrases like ‘an old biddy’.
Cassidy refuses to accept the well-known explanation associating it with the name Bridget. His claim is that it comes from the Irish word beadaí, both a noun meaning an epicure or a fastidious person and the adjective for fussy or fastidious. It can also mean ‘a goose’. Beadaí is pronounced ‘baddy’ and its meaning of fastidiousness has nothing to do with the English meanings of the word biddy. Old biddies are usually gossips and busybodies, not fussy people.