The song was presumably in vol 3 of Songs of the North; it isn't in the first two, at any rate. Harold Boulton wrote a lot of songs that are often passed off as "traditional" nowadays (see previous discussions on 'Castle of Dromore', for example), and these were often set to older, sometimes traditional, tunes; though he wrote some tunes as well, most notably (from our point of view) the melody to which 'The Lyke Wake Dirge' is nowadays sung.

What Boulton didn't do was write in, or translate from, Gaelic; Andy M Stewart was quite wrong to say that. Unfortunately that error has by now been repeated all over the place. He worked in the same area of songwriting as did Thomas Moore and Albert Percival Graves, both of whom also wrote a lot of stuff that is resolutely claimed as "ancient" and "traditional" by people who are too lazy to do a little basic research.

The excuse made by 'Silly Wizard' is a bit feeble; Boulton only died in 1935, and when they recorded his song it was barely out of copyright.