www.alphadictionary.com

I've had this one on my list of suggestions for the suggestion list for a while now. Perhaps it's time to make the suggestion.

I always understood this word as meaning awkward, goofily clownish, etc. Come to find out it means aggressively, rudely, or offensively assertive. I believe I conflated it with bumpkin, which is often used to describe a palooka from Podunk.

Apparently different derivations here, possibly related to bump. Still it's an amusing word, and it's easy to think of a bumptious bumpkin bumping palookas.