| 1 | Latin | Caligula | — |
| 2 | Latin | caliga | Leather shoe or boot; second-person singular... |
| 3 | Latin | -ula | regō + API → rēgula; tegō + API → tēgula;... |
| 4 | Proto-Indo-European | -tlom | Alternative form of *-trom |
| 5 | Proto-Indo-European | -trom | Forms nouns denoting a tool or instrument |
| 6 | Proto-Indo-European | -tḗr | Derives agent nouns from verbs, denoting someone... |