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, in his etymological hoax, How The Irish Invented Slang, the slang term shindig comes from the Irish expression seinnt-theach, meaning a house of music. Seinnt is a common variant of seinm, which means to play a musical instrument, and teach does mean house but the expression seinnt-teach is complete fabrication. It is not attested in Irish and there are a lot of familiar phrases for a house where music is played and people gather for entertainment, such as teach céilí, teach airneáil, teach airneáin. Teach ceoil (house of music) would also sound reasonable and any Irish speaker would know what you meant. But seinnt-teach (you wouldn’t aspirate the teach, as Cassidy does, so his version of seinnt-theach is a misspelling anyway) is not a real word and it sounds very odd, as if the house is an instrument and someone is blowing into it or hitting it. If you know Spanish, the phrase casa de tocar would give you some indication of why it is odd and improbable.
Interestingly, Loretto Todd, in her 2000 book Green English, suggests that shindig might derive from sínteach, a Scottish Gaelic term for generous. This is also highly improbable.