Lummox \LUHM-uhks\ , noun;
1. A clumsy, stupid person
This word dates to 1825 as East Anglian slang. As a slang term, it's origins are uncertain, but it's probably either taken from dumb ox with influence from lumbering, or it's a dialectal form of lummock ("move heavily or clumsily").
Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Sunday, October 16
Etymologies come from the Oxford English Dictionary and/or Etymonline.com