proofproof

Proof comes from Middle English proof, from Old French prove, from Late Latin proba ‘a proof’, from Latin probō ‘to test, prove’.

1. Proto-Indo-Europeanc. 4500–2500 BCE*pro-bʰH-wó-s¹‘being in front’reconstructed
2. Proto-Italicc. 1500–700 BCE*proβos²‘correct, proper’reconstructed
3. Proto-Italicc. 1500–700 BCE*proβāō¹‘to approve’reconstructed
4. Latinc. 75 BCE–200 CEprobō²‘to approve; to test’
5. Late Latinc. 200–600 CEproba²‘a proof’
6. Old Frenchc. 842–1400prove²
7. Middle Englishc. 1150–1500proof²
8. Englishearliest quotation 1590proof²

1. ¹ Wiktionary, Latin probo
2. ² Wiktionary, English proof
3. Earliest quotation in Wiktionary’s entry: 1590, Edmund Spenser, Book III, Canto I: “But the chaste damzell, that had never priefe /…”.