Thanks for all the replies, especially those from Annie and Maeve. I'm confused by a couple of other replies though:

In one post, "Good Soldier Schweik" writes "jockie is scotsman" – but earlier in the thread, Abby Sale wrote that a jockie was specifically a Scots country lad. In the context of this song, which is more accurate? (I.e. did the author mean to convey that the singer was from the countryside or just that he was from Scotland?)

In another post, "gutcher" writes: "Kail was the generic name for soup---usually broth." That confuses me on two counts: in every version of the song I've seen, it's spelt "kale", not "kail"; and earlier in the thread, "Murray on Saltspring" wrote "kale = cole, or cabbage". In the context of this song, which translation is more likely to be accurate - cabbage, or broth?

Dave