Where does “lest” come from?

lest (Middle English) comes from Old English læste, from Proto-Germanic laistiz, from Proto-Indo-European leys- — to trace, to track.

Ancestry of “lest”, step by step

StepLanguageWordMeaning
1Old Englishlæstelast
2Proto-Germaniclaistiz—
3Proto-Indo-Europeanleys-to trace, to track
Every word from Proto-Indo-European leys- →Every word from Proto-Germanic laistiz →Every word from Old English læste →