Steve wrote:

'Fenian Men could be a minor variant of the HotM tune.

If I remember rightly the songs 'Knife in the Window' and HotM are actually 2 separate songs that got spliced together in Somerset some time in the 19th century.'

As luck would have it, I've just done a study of this song, and the answers to both of these questions are in the version Sharp collected from John Barnett in Bridgewater in 1906, which has the minor tune that sounds like 'Bold Fenian Men' and contains five stanzas of 'Knife in he Window' plus three of HotM (blackbirds, hares, ducks).

Roud catalogues both songs under #329, and Sharp's titles in his MS indicate that he thought they were one and the same song: there are other versions in Sharp and Hammond that begin with a 'Sally, my dear' verse and then proceed into 'Hares'. In the US there are versions of 'Knife' and 'Hares' that share the 'Lay your leg over me' chorus.

There's a US version from the Max Hunter archive online here, with an interesting variant on the 'hare' verse:

If all the young ladies were little white rabbits
I'd be a hare an' teach them bad habits
Roll your leg over, roll your leg over
Roll your leg over the man in th moon