| 1 | English | -proof | Used to form adjectives denoting an impervious or... |
| 2 | English | proof | An effort, process, or operation designed to... |
| 3 | Middle English | proof | — |
| 4 | Old French | prove | — |
| 5 | Latin | proba | test, trial; proof, evidence |
| 6 | Latin | probāre | — |
| 7 | Latin | probō | — |
| 8 | Latin | Probus | — |
| 9 | Proto-Indo-European | pro-bhwo- | being in front, prominent |
| 10 | Proto-Indo-European | pro- | toward, forward |
| 11 | Proto-Indo-European | por- | to give birth; forward, through; going, passage |
| 12 | Proto-Indo-European | per- | before, in front; first; to go through |
| 13 | Proto-Indo-European | pr̥tós | passed , crossed |