Ignoring that...

the first trace of this song (*this* song, not "Hares on the Mountains") appears to be from World War II, as sung by American marines in the Pacific.

And in my experience, all known versions seem to descend from LPs made by the popular Oscar Brand in the 1950s, with cleverer stanzas continually added.

True? Does anyone know a version of "Roll Your Leg Over" actually learned in the 1940s?

(The opening bars sound a lot like "St. Patrick's Day.")