Showing too much enthusiasm or eagerness in a way that's excessive or annoying.
Prefix 'over-' (too much) plus 'zealous' from Greek 'zelos' (fervor). Literally means enthusiasm that has crossed the line into being too much.
Ancient Greek culture celebrated 'zelos' as a divine quality—it was one of the good passions—but overzealousness showed how even the ancients knew too much of a good thing could be destructive.
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