In his ridiculous book How The Irish Invented Slang, Daniel Cassidy claimed that the word wallop, meaning to beat or strike, is derived from the Irish bhuail leadhb.
The first thing that needs to be pointed out about this claim is that bhuail leadhb is not a proper Irish phrase. Bhuail is the past tense of buail meaning to beat. Leadhb, amongst other things, can refer to a blow or a stroke, but in this sense it is usually used with the word for give – thug sé leadhb dó, he gave him a blow, not bhuail sé leadhb (air?). (This is much the same as English – you don’t beat someone a blow, you beat someone or you give someone a blow.) And bhuail leadhb would never be heard together, because it needs a subject, (bhuail sé leadhb, bhuail Pádraig leadhb) and nobody would borrow a phrase unless they heard it being used, which they wouldn’t with bhuail leadhb. I should also point out that Cassidy claimed bhuail as the origin of wale as well. So the same word becomes wale in one case and wall in another, which is hardly likely.
Furthermore, wallop is an ancient word in English, though it originally meant to gallop. It apparently only acquired the new meaning of to beat or strike in the early 19th century, but this is probably a development of its earlier meaning, or perhaps just a re-use of a word which sounded right for a blow. Wherever it genuinely comes from, the fact is that it doesn’t come from bhuail leadhb, which was invented by a non-Irish-speaking lunatic in California circa 2005.