If you re-read Bruce Olson's quotes you might agree with me that they do not at all make it clear that "rumbelo" or "rumbylow" are places. Skeat does not print "rumbelow" in what has become the accepted spelling of this word in "Hal and tow". However, there is no official orthography with such non-standard words, and there was certainly comparatively little recognised orthography in the 18th C and earlier. Consequently we have to take a common-sense approach to questions of this sort. If you can accept, for instance, Olson's "rumbelo" as being a relation of the word in "Hal and tow", I fail to see why a connection cannot also be made between Smollett's "rumbo" and Skeat's "rumbowling".