Rumbelow:
Not extant is the tale or song "sal i go vitht zou to rumbelo fayr?" noted in 'The Complaynt of Scotland'', 1549.
Fabyan's chrohronicle has it in the burden of a ballad on the battle of Bannocokburn, 1314,
Maydins of England
........
So soone to have wonne Scotlande,
Wyth rumbylow
Comentators, the few who bother to note it, usually pass off Rumbelo as a non existant place. The choruses of some ancient songs have a boatman (named Norman in one such) rowing to Rumbelo, so it seems it was an island.
I suspect it was another name for Atlantis or some other Shangrila from a tale or song that has not survived, but I don't have any solid evidence for this after watching for some for over 30 years now.