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.
Jerk, a slang term for “tedious and ineffectual person,” first appears in American carnival slang in 1935. Its origin is uncertain, but it possibly derives from jerkwater “petty, inferior, insignificant”. This term goes back to the days of steam trains, when the water for the steam engine needed to be replenished regularly. In small towns, they needed to form a human chain and “jerk” the water (i.e. lift it on a rope) to fill the engine. Thus a small, hick town was known as a jerkwater town. (Some experts say that jerking water refers to a system whereby water was lifted while the train was in motion, but this doesn’t change the basic argument, that jerkwater is a railroad term for an insignificant town). This may have also been influenced by the phrase jerk off, referring (for obvious reasons) to masturbation.
These are the facts. Daniel Cassidy, in his book How The Irish Invented Slang, claimed that this word derives from déirceach. Déirc is the Irish for alms and a déirceach can be either a beggar or a person who gives out alms, and Cassidy makes much of the fact that both beggars and charity-givers (many of whom offered starving people food in return for a nominal religious conversion in Ireland) were both regarded as jerks by the Irish. If this were the genuine etymology, this speculation might be of interest, but déirceach is not a common word and especially not in the sense of beggar, which is usually bacach in spoken Irish. There is absolutely no reason to suppose that déirceach is the origin of the American English jerk or has any connection with it.