Designed or sealed so that dust cannot enter or escape; resistant to dust infiltration.
Compound of 'dust' and 'proof' (from Old French 'prove', meaning test or trial). The '-proof' suffix (meaning impervious or resistant to) became productive in English during the 19th-20th centuries, creating words like 'waterproof' and 'fireproof'.
The 'proof' in 'dustproof' doesn't mean evidence—it's the same root as 'proven,' implying something has been tested and found resistant. This suffix became wildly popular when factories needed to describe protective products.
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