Spencer was confused (first verse) but probably hadn't been away for a very long time. His wife was surprised, but the children seem to have taken it in their stride in broadside versions. In sets from oral currency, the whole family was often amazèd, but probably only because they weren't expecting him.

Black Velvet Band (originally set in London) was later localised (among other places) both to Tralee and Belfast. Both forms were popularised through commercial recordings during the 1960s, and no doubt people who learned them later on muddled them up sometimes.

Inconsistency is part of the deal, really, when dealing with tradition. Sometimes it's built in, sometimes it's the result of misunderstanding. Christmas in the Trenches is a modern song, so I wouldn't consider it particularly relevant; though it does illustrate that if you don't think carefully enough when writing, it may come back to haunt you.

Mind you, God's in France all Sunday.