Anne: toom [which you will find in Chambers Dictionary] has a short middle oo, more like the N Country pronunciation of Mum [or thumb, for that matter — think how a Yorkshireman would say 'rule of thumb'], than of 'gloom'. & I don't quite see how 'empty un' would easily corrupt to 'tyum', which lacks the entire first syllable and ends with a different consonant. So, Occam-wise, I still think my explanation the more simple, if you accept that the u would be pronounced North Country-wise.

The line you quote of the bridegroom dangling his bonnet and plume is from 'Lochinvar', which was Scott's reworking of the traditional ballad of Katharine Jaffray [also in Child, #221].

I think 'Jowl & Listen' & 'Rap her to Bank' are related songs which share some 'floaters', aren't they?

Regards - Michael Grosvenor Myer