| 1 | French | officieux | unofficial |
| 2 | Latin | officiōsus | — |
| 3 | Latin | officium | duty, service; office; obligation, an obligatory... |
| 4 | Latin | opificium | work |
| 5 | Latin | opifex | Someone who does work ; worker, maker, framer,... |
| 6 | Latin | Ops | earth goddess, fertility deity |
| 7 | Latin | oscen | any bird by whose song cries augurs divined... |
| 8 | Latin | opscen | — |
| 9 | Latin | ob- | towards; against |
| 10 | Latin | obolus | obolus |
| 11 | Ancient Greek | ὀβολός | obol, obolus, used at Athens as both a weight and... |
| 12 | Ancient Greek | ὀβελός | a spit, rod; a horizontal line |
| 13 | Ancient Greek | βέλος | missile, arrow, dart; weapon; something quickly... |
| 14 | Proto-Indo-European | gʷélHos | — |
| 15 | Proto-Indo-European | gʷelH- | to throw, reach, pierce; to hit by throwing |