To take for granted or suppose something is true without proof; to take on a role, responsibility, or appearance. To adopt or put on.
From Latin 'assumere' meaning 'to take up, adopt', from 'ad-' (to) and 'sumere' (to take). Originally meant physically taking or adopting something, but evolved to include mental acceptance of ideas without proof.
The word 'assume' contains a warning in its very structure - when we 'assume' we literally 'take up' an idea without proper foundation, which is why assumptions can be dangerous. The phrase 'assume makes an ass of u and me' plays on this inherent risk of taking things for granted.
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