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.
There is no agreement about the origins of the word hip (in the sense of cool, trendy, not as in the thing at the top of your leg). You can find a discussion of the word here: https://en.wikipedia.org/wiki/Hip_(slang)
The late Daniel Cassidy, in his work of fake etymologies, How The Irish Invented Slang, claimed that hip and its earlier form hep derive from the Irish word aibí (or abaí). Cassidy defines this word as:
Aibí (pron. h-abí; contraction h-ab’), adj., mature, quick, clever, quick-witted; fig. wise.
As usual, this is arrant nonsense. The word is defined by Ó Dónaill as ‘ripe, mature; quick, clever; crisp’. Its primary meaning is ripe. Dinneen defined it as ‘ripe, mature, quick-witted’. It does not mean wise, it is not pronounced with a h-, and while it is conceivable that a short vowel at the end of a word would be lost in speech, there is no reason to suppose that this would ever happen to a long vowel like the -í at the end of this word. The word is pronounced abbey or appee or abwee, depending on dialect (this is why it is sometimes spelled abaí). Why would appee or abwee become hip or hep? Wherever the word hip came from, it didn’t come from Irish and as it’s associated with African-American culture, it seems more likely that its roots, whatever they are, lie there.