| 1 | Middle English | couth | known, familiar; familiar, known; evident, true;... |
| 2 | Old English | cūþ | known; familiar, intimate, known, usual; certain,... |
| 3 | Old English | cunnan | to know, to be familiar with; can, to know how |
| 4 | Proto-West Germanic | kunnan | to recognise; to know how, to be able |
| 5 | Proto-Germanic | kunnaną | to know, to be familiar with, to recognise; to... |
| 6 | Proto-Indo-European | ǵneh₃- | to know |