Also called John Reilly, yes; sometimes, and among many other names. Completely irrelevant to the song asked about, except insofar as people who don't realise that different songs may sometimes share a title might become confused, so it was worth mentioning as a pre-emptive measure; though I'm not too confident that everyone will understand that it was meant as such. "John Reilly" (various spellings) is a very common name, of course; we should all be thankful, I suppose, that it wasn't "John Smith".