Something strange, unusual, or peculiar; or a person who behaves in an unusual way.
From Middle English 'odde' meaning 'odd number, leftover', from Old Norse 'oddi' (point or angle). The sense evolved from mathematical oddness (unpaired numbers) to general strangeness.
The word 'odd' originally meant something left over—like if you had 7 items and divided them in pairs, 1 would be 'odd' because it didn't have a partner. That's why 'odd' gradually came to mean strange or unusual.
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