The story
- French · derived froms'il n'était pas mort, il ferait encore envie
- English todayLapalissian
From Jacques de la Palice (a French nobleman and military officer) + -ian. His epitaph, carrying the words “if he weren't dead, he would still be envied” (French s'il n'était pas mort, il ferait encore envie), was misread as the truism “if he weren't dead, he would still be alive” (s'il n'était pas mort, il ſerait encore en vie).
Etymology from Wiktionary, CC BY-SA 4.0.