- proof
- early 13c., preove "evidence to establish the fact of (something)," from O.Fr. prueve (early 13c.), from L.L. proba "a proof," a back-formation from L. probare "to prove" (see prove). Meaning "act of testing or making trial of anything" is from late 14c. Sense of "tested power" led to fireproof (early 17c.), waterproof (1736), foolproof (1902), etc. Meaning "standard of strength of distilled liquor" is from 1705. Typographical sense of "trial impression to test type" is from c.1600; proofreader first attested 1832. Numismatic sense of "coin struck to test a die" is from 1762; now mostly in ref. to coins struck from highly polished dies, mainly for collectors.