This one I think I can get pretty much right without resort to the Internet:
Boomhower is one of those occupational names that were probably altered in spelling when the bearer came over from Europe (or during World War I to avoid prejudice -- very common). In German, Boomhower would be "Baumhauer" -- literally a "tree hewer", so a woodsman or lumberjack by trade.
In form, "Boom" is the correct spelling for "tree" in Dutch, but I'm not very confident that "hower" In any spelling is a Dutch equivalent to "hauer". (Anyone know better?) But if it is, the derivation could be Dutch instead of German.
A parallel name that was changed in America would be "Eisenhower", which in German means (I think) not "iron cutter" but "iron miner", since the words for "miner" and "hewer/cutter" vary by only one teensy umlaut over the "a".
Jog my memory: wasn't Boomhower the ROTC frat jerk in "Animal House"?