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.
Daddy-o is an expression used from the 1950s onwards by hipsters and beatniks. It is simply a term of endearment. Cassidy believes that it derives from the Irish word daideo, which is pronounced dadge-oh and means grandfather. There is no reason to suppose that daddy-o is anything other than daddy with o on the end of it. There is an interesting piece of dishonesty in Cassidy’s treatment of this. He claims that daideo is pronounced dad’ǝo, and therefore that it has a diphthong at the end, as in the English expression. This is not true.