Apparently some German in there too. Etymology From Old French lesser, lessier, laissier (“to let, let go, leave”), from Latin laxō, laxāre (“to relax, loosen”

Apparently some German in there too. Etymology From Old French lesser, lessier, laissier (“to let, let go, leave”), from Latin laxō, laxāre (“to relax, loosen”); partly from or influenced by Old High German lāzan (“to let, let go, leave”) (German lassen), from Proto-West Germanic *lātan (“to let, leave, leave alone”). I can't find anything about it and I've been poking around for the better part of 20 minutes, but my presumption would be this comes from Royal Court, to take leave of the court or the presence of the Royal estate? I'm guessing you would be granted permission to take your leave > take leave > permission. Total guess, however. Who knew leave could be so fun. ;)