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.
The word dinger is from Middle English and probably derives ultimately from a Scandinavian language. Cassidy claimed that dinger comes from dianmhaith. This is an adjective and it derives from maith, which means good. The word dian is an intensifier. Dianmhaith would be pronounced jeeanwoy in the north, and deeanvah in southern dialects. Neither of these sound much like dinger. Cassidy also claims that humdinger comes from iomar-dianmhaith, with a further intensifier, iomar-, attached. If this were the case, it would really be iomar-dhianmhaith, which would be pronounced umar-yeeanwoy or umar-yeeanvah, which don’t sound anything like humdinger.
In reality, humdinger and dinger are derived from an English dialect term ding, which meant ‘to strike, push, hurl, batter, or bruise with energy, wrath or forcefulness.’ By extension, the word dinger could mean anything of a superlative character – ‘It’s a dinger!’
You can find more information on this here: