Words at Play : Top 10 Rare & Amusing Insults, Vol. 2
Definition:
lout; a stupid, rude or awkward person
About the Word:
Loblolly was originally a British word for "a thick gruel." Riffing on this, apparently, Americans later used the word to refer to an ugly, boggy mess.
It's unclear how the word developed its insulting sense, but perhaps the evolution was similar to the current use of words like thick and dense to mean "stupid."