Where does “goon” come from?

I appreciate the detailed instructions, but I notice there's a mismatch in your request. You've asked me to write an etymology for the headword "goon" but provided an etymological chain for "flagon." Could you clarify: should I write the etymology summary for **flagon** (using the chain you provided) or for **goon** (which would require a different chain)? Once you confirm which word you need, I'll write the one-sentence summary following all your specifications.

goon (English): A thug; a usually muscular henchman with little...