Discussion Forum—A Way with Words, a fun radio show and podcast about language

I'm curious what some of the experts here think of the series on the History Channel called "America's Secret Slang." For those who haven't seen it on television yet, full episodes of the first two seasons are also currently viewable on the History Channel website for free. However, a subscription is necessary to see through the tablet/phone app. 

Origin reasoning for expressions are given straight forwardly as fact, so it would seem that some explanations might be open to controversy. The main expression that I became curious about, because of the contradictory opinion of Grant and Martha is the origin of "cry uncle."

In one of the first season's episodes, "Coming to America," the show posits the influx of Gaelic speaking Irish immigrants as the origin including such expressions as "full of baloney," "longshoreman," "dogie," "cop," "nincompoop," and "cry uncle." These were based on the theories of author Daniel Cassidy in his book "How The Irish Invented Slang." He avers that uncle, in this sense, came from the Gaelic "anacal," (loosely pronounced ahna-kaal) which means mercy. This makes sense, because the language predates the parrot joke explanation, is straight forward, and would be something a Gaelic speaker would say if he had enough in a fight or the dominator would ask his victim to say. Also the parrot joke explanation seems too contrived in its reasoning because of its transference from America back to England instead of from Ireland to England, as the unique word the owner was trying to get the parrot to say and the reason why the parrot fought with the chickens. Where else has a joke been the origin of an expression, anyway?

Why is the Gaelic origin of this expression discounted?

Anyway, back to the original question. Did anyone else take issue with any other word origins or the validity of its authoritative stance, in this show series?