| 1 | Old English | clacian | to clack, clap; to chirp, tweet |
| 2 | Proto-Germanic | klakōną | to clap, clack; to chirp, tweet, twitter |
| 3 | Proto-Indo-European | glag- | to make a noise, clap, twitter; to make a noise,... |
| 4 | Proto-Indo-European | gal- | to call, cry; to sound; to roop, scream, shout |