| 1 | English | casual | Happening by chance; Coming without regularity;... |
| 2 | Middle French | casuel | fatal; of or relating to chance or fate |
| 3 | Late Latin | casualis | happening by chance; fortuitous; casual |
| 4 | Latin | casus | a fall, downwards movement; accident, chance; an... |
| 5 | Latin | cadere | present active infinitive of cadō; to fall, to... |
| 6 | Latin | cado | I fall, I fall out; I die; I cease |
| 7 | Proto-Italic | kadō | fall, sink |
| 8 | Proto-Indo-European | ḱad- | to fall |