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.
Anyone with any sense would realise that there is a clear connection between the noun quirk and the adjective quirky. As we have pointed out before, it is a measure of how irrational and lacking in common sense Cassidy was that he tended to look for different Irish origins for such obviously related words in English.
In this case, Cassidy regarded the noun quirk as being from the Irish adjective corrach, meaning rough, unstable or uneven, while to him, quirky came from another adjective, corraiceach (with the same meaning of unstable or rickety) or else from corrchaoi, which means ‘an odd way’. Corrach is pronounced korrah and sounds nothing like quirk. There is also a problem in the idea of an adjective in Irish giving rise to a noun in English.
In reality, while we cannot be sure about the origin of the term quirk, it dates back to the 16th century in English and seems to be a technical term for a twist or flourish in weaving. From this, it came to have the metaphorical meaning of a peculiarity in a person or a work of art. This makes a lot of sense, when you consider that a quirk of fate is the same as a twist of fate. It certainly makes more sense than it deriving from Irish words like corraiceach or corrach.