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.
The experts tell us that raspberry (as in ‘to blow a raspberry’) is rhyming slang and comes from ‘raspberry tart’ = fart. This seems to have emerged in the capital of rhyming slangs (London) in the 1890s and spread fairly quickly throughout the English-speaking world.
According to the late Daniel Cassidy in his etymological hoax, How The Irish Invented Slang, raspberry comes from the words raiseadh (sic) búirthí, which translates roughly as a volley of bellowings. Of course, blowing a raspberry means to make a farting noise with the lips, so an Irish speaker would use the word broim (fart)or some variant of it to describe the action of blowing a raspberry, not a word meaning a barrage of bellowing.
Of course, there is no evidence of anyone, anywhere actually using the phrase roiseadh búirthí before Cassidy. Focloir.ie gives broim béil (a mouth-fart) as the Irish for a raspberry in this sense.