| 1 | English | fretful | Irritable, bad-tempered, grumpy or peevish;... |
| 2 | English | FRET | Förster resonance energy transfer; fluorescence... |
| 3 | Middle English | frēten | to eat; to devour, eat up; to bite, chew; to... |
| 4 | Old French | freter | to fret |
| 5 | Old French | fret | charge; past participle of fraindre |
| 6 | Middle Dutch | vrecht | Alternative form of vracht; cost of transport |
| 7 | Old Dutch | frēht | — |
| 8 | Proto-Germanic | fra- | off, away; completely, fully, up |
| 9 | Proto-Indo-European | pro- | toward, forward |
| 10 | Proto-Indo-European | por- | to give birth; forward, through; going, passage |
| 11 | Proto-Indo-European | per- | before, in front; first; to go through |
| 12 | Proto-Indo-European | pr̥tós | passed , crossed |