And I would repeat my suggestion that that was probably an entirely imaginary "meaning" recently imposed on a perfectly straightforward song by people who didn't know what they were talking about, but who made unwarranted assumptions based purely on the colour of one of the dogs and an assumption that it "must" be a Irish song with a hidden subtext. The "happy guessers", as the Opies called them, are still at work. They are at liberty to believe anything they like, however unlikely (and this is very unlikely indeed); but not to present it as fact.

The song may be Irish, of course; but there seems to be no record of it in Ireland prior to the spread of Jack Elliott's version (currently on its own at number 12934 in the Roud Folk Song Index, but see below) via the folk clubs and Bob Davenport's recording of it. Until or unless evidence to the contrary comes to light, my money is still on a music hall origin, whether British or Irish; and I would be astonished if there were anything more to it than that.

Roud 3495 ('Twenty-Pound Dog') also includes a print example of Elliott's version, and three American sets collected in the early 1940s. There is also an unclassified American example recorded in 1937 ('The Twenty Pound Bulldog'; the earliest date we have so far for the song) listed at the Library of Congress (see link above). These references will need to be pulled together under a single heading at some point.