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.
There is no consensus about the etymology of the term uncle in the expression ‘Say uncle!’ (Equivalent to ‘Pax!’ in English or ‘Méaram!’ in Irish.)
The most likely explanation is an oft-repeated joke about a parrot: A gentleman was boasting that his parrot would repeat anything he told him. For example, he told him several times, before some friends, to say “Uncle,” but the parrot would not repeat it. In anger he seized the bird, and half-twisting his neck, said: “Say ‘uncle,’ you beggar!” and threw him into the fowl pen, in which he had ten prize fowls. Shortly afterward, thinking he had killed the parrot, he went to the pen. To his surprise he found nine of the fowls dead on the floor with their necks wrung, and the parrot standing on the tenth twisting his neck and screaming: “Say ‘uncle,’ you beggar! say uncle.’ ”
Apparently, this joke (however unfunny it seems to modern taste) was often printed in newspapers in the 1890s in Britain and in the USA. Another explanation is that Say uncle! comes from a Latin phrase used by Roman children, who customarily said “Patrue, mi Patruissimo,” or “Uncle, my best Uncle,” in order to surrender to a bully. I have failed to find any confirmation at all of this claim.
According to Daniel Cassidy, this comes from the Irish anacal, meaning ‘mercy, quarter; fig. surrender’. I need hardly say that the surrender bit was added by Cassidy and isn’t a real definition of the word. There is no evidence of anyone asking for mercy using the old-fashioned and rather literary word anacal in playground games.
In any case, this claim was made first in American Speech vol 51, 1976, though Cassidy doesn’t mention this in his book. In other words, the claim of a link between anacal and uncle dates back thirty years before Cassidy’s book.