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.
It seems that this use of whale as a verb meaning beat or whip first occurs in the late 18th century and it has been suggested (quite reasonably) that it comes from the word wale, to mark with wales (variant of weals) or stripes, which has been used since the 15th century.
Daniel Cassidy, in his etymological hoax, How The Irish Invented Slang, claimed that this word comes from bhuail, the past tense of buail, meaning hit. As I have said before, words and phrases are not just borrowed randomly between languages and the link between whale and bhuail is highly improbable.