Refrains can mutate from sense to nonsense or vice versa.

For example, the Geordie version of The Herring has "How are ye the deea" x 3, but a version from the NE of Scotland (as sung by Isla St Clair - dunno who she got it from) has "Falalalido" x 3, which does bear some resemblance in sound and which I therefore suspect results from corruption of the Geordie version.

Part of the chorus of "Nutting Girl" is generally sung "Whack fol the dear oh day" (approximately) but can be "Wait for the dear all day" which actually makes sense.

Richard