As described in historical dictionaries

Patronymica Britannica (1860)

RUM. " Rum," says Mr. Ferguson, " I take to be from 0. Norse runu', vir miraanis, gigas — one who might truly be called a "rum customer." Hence may indeed be the origin of our word ritm for queer, which appears indigenous to some of oar northern dialects, and which I doubt, therefore, being a cant phrase." Rum is also an old pei"soual name mentioned by Neunius : Rum map Urbgen. Mou. Uist. Brit., p. 7G.

Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.


BritishSurnames.uk is a Good Stuff website.