Daniel Cassidy (sometimes known as Professor Daniel Cassidy, though it is clear that he was underqualified to be a professor of anything) was the author of an insane work of pseudo-scholarship called How The Irish Invented Slang, in which he claimed that hundreds of English words were really derived from Irish. For example, he claimed that the word taunt is derived from the Irish tathant, which means to urge or incite or entreat.
There are several problems with this. While taunt sounds a bit like tathant (tahunt), the word taunt is already found in the English of England at the beginning of the 16th century. This is too early for it to have come from Irish, as there was no significant Irish immigration to England that far back. Furthermore, most scholars regard it as from French, probably from tenter (to tempt or to provoke). And then again, the meaning is off. Tathant is a word with positive connotations. It means to urge, to encourage, to entreat, not to rile someone or provoke them.
This is yet another piece of childish non-scholarship and yet another piece of evidence that Cassidy, far from being a serious academic, was the perpetrator of intellectual fraud on an industrial scale.