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.
According to the late Daniel Cassidy, the exclamation Hot Dog! comes from the ‘Irish’ phrase árd-tach, which he defines as ‘loud oath! Loud declaration, as in “I declare!” Fig. Curses!
As we have seen with related expressions, the element -tach is an ancient legal element which forms part of many expressions in ancient Irish law relating to swearing or affirming. It has not existed as an active part of the language for many centuries, and the idea that you can simply stick -tach on the end of a word to form a new word is ridiculous.
This is not a genuine Irish phrase. It was made up by Daniel Cassidy.