Meaning

noun any factual evidence that helps to establish the truth of something

noun a formal series of statements showing that if one thing is true something else necessarily follows from it

noun a measure of alcoholic strength expressed as an integer twice the percentage of alcohol present (by volume)

originFrom Middle English proof, from Old French prove, from Late Latin proba (“a proof”), from Latin probō (“to prove”); see prove; compare also the doublet probe.

Etymology from Wiktionary, CC BY-SA 3.0