I thought right away they sounded similar, but had to actually think about it to realize it was both names mixed up. Btw, in japanese there's no written m, but you pronounce it depending on the next syllable, so a better translation would probably be Dumbalf (yeah sounda dumb).
From what I remember of the LN, the MC straight up named his character after his two favorite wizards, referencing a school chairman and a quest involving a ring...