Resembling or characteristic of a rooster; arrogant or swaggering like a rooster.
From 'cock' + '-ish' (adjective suffix meaning 'resembling or having qualities of'), created in the 1600s-1700s.
The suffix '-ish' is brilliant for creating insults—'cockish,' 'foolish,' 'knavish'—because it lets you compare someone to an animal or negative quality, which is more colorful than just saying 'you're bad.'
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