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 Daniel Cassidy, this American slang word for a timid gambler, a stingy person or a vagrant comes from the Gaelic word picear. There are actually three possibilities here, as far as I can see.
Firstly, that piker is related to the insulting slang term for a traveller (Gypsy) pikey, which is probably from pike, a shortening of the term turnpike, which meant a toll road, perhaps reinforced in America by an association with Pike County, and that this word then entered Scottish Gaelic as picear.
Secondly, that picear is from some unknown source in Gaelic and that it then spread into English as piker, just as Cassidy claims.
Thirdly, that picear derives from the Scots and English dialect word picker, meaning a petty thief, and that it is unconnected with the English slang term piker.
As picear is pronounced like picker and not like piker, the third option seems by far the most likely.