Thanks FreddyHeadey for the link to the earlier thread.

Many of the comments in both threads refer to Bow in London or in general to bows in rivers, but "bow" in that sense rhymes with "toe". In the version I got from Pete Nalder, "bow" rhymes with "how". (Curse the vagaries of English spelling.)

Any thoughts on which of those pronunciations may have applied to the refrain in the Scots versions in Child?