'ant-proof' originates from Modern English as a compound of 'ant' + 'proof', where 'ant' refers to the insect 'ant' and 'proof' (here a combining element) means 'resistant to' or 'protective against'.

'ant' derives from Old English (e.g. 'ǣmete' / 'æmete') related to German 'Ameise', while 'proof' as an element (meaning 'resistant to') developed in English from Old English/Old French roots (Old French 'preuve' < Latin 'probare' 'to test/prove'); the compound form 'ant-proof' is a straightforward modern English formation.

The components originally referred separately to the insect ('ant') and the idea of testing/proving ('proof'); combined in modern usage they straightforwardly mean 'resistant to ants' with little semantic shift beyond compounding.