Resistant to or protected from damage caused by drinking or spilled drinks; able to withstand liquid damage.
From English 'drink' (Old English 'drincan') + 'proof' (from Old French 'prove' meaning 'to test'), forming a compound meaning 'resistant to drink-related damage.'
The '-proof' suffix comes from the way alcohol was once tested by pouring it on gunpowder—if it ignited, the spirit was 'proof'—and now we use it for anything designed to resist damage, from waterproof to childproof.
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