| 1 | Italian | occasionalmente | fortuitously, by chance; occasionally, sometimes,... |
| 2 | Italian | occasionale | occasional, chance; casual, odd |
| 3 | Italian | occasione | opportunity, chance, occasion, scope;... |
| 4 | Russian | оказия | opportunity; unexpected event |
| 5 | Polish | okazja | — |
| 6 | Latin | occasio | occasion, opportunity; kairos, the right time,... |
| 7 | Latin | occasus | setting; west; western |
| 8 | Latin | occidō | — |
| 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 |