lethal

lethal · adjective, noun¹

1. Latin · learned borrowing fromlētālis“deadly, mortal, fatal”
2. English todaylethal

Learned borrowing from Latin lētālis (“deadly, mortal, fatal”), improperly written lēthālis, from lētum (“death”), improperly written as lēthum, from a supposed connection with Ancient Greek λήθη (lḗthē, “oblivion, forgetfulness”).

lethal · noun²

Abbreviation of “lauric acid ethereal salt”, so called because it occurs in the ethereal salt of lauric acid.