Where does “lat” come from?

lat (Middle English) comes from Old English læt, from Proto-Germanic lētaz, from Proto-Germanic lētaną, from Proto-Indo-European leh₁d- — to be tired.

Ancestry of “lat”, step by step

StepLanguageWordMeaning
1Old Englishlætslow; slack, lax, negligent; late
2Proto-Germaniclētazfreeman; bondsman; serf
3Proto-Germaniclētanąto let, to allow; to leave alone
4Proto-Indo-Europeanleh₁d-to be tired
Every word from Proto-Indo-European leh₁d- →Every word from Proto-Germanic lētaną →Every word from Proto-Germanic lētaz →