| 1 | Latin | congratulatio | — |
| 2 | Latin | congratulor | I wish joy; I rejoice with; I congratulate |
| 3 | Latin | cōn- | — |
| 4 | Latin | cum | with, along with; at; -fold |
| 5 | Old Latin | com | Alternative form of cum |
| 6 | Proto-Italic | kom | with, along, at |
| 7 | Proto-Indo-European | ḱóm | beside, near, by, with |
| 8 | Proto-Indo-European | ḱe | Deictic particle, here; Post-positional... |
| 9 | Middle English | kyt | — |
| 10 | German | kitt | — |
| 11 | Old High German | kuti | — |
| 12 | Proto-West Germanic | kwidu | gum, resin |
| 13 | Proto-Germanic | kweduz | resin |
| 14 | Proto-Indo-European | gʷet- | resin, gum; to say, speak |
| 15 | Proto-Indo-European | gū- | to bend; curve; arch; vault; to bow, bend, arch,... |