When did level grinding become a thing in computer games?

So, Lis is grinding away at a game she's playing and was wondering -- when did grinding levels become a thing that can be done? You need to have a situation in which you become more powerful as you play, by levelling up, getting better equipment, practicing skills, or whatever, and you need to have the ability to replay lower levels so that you CAN keep doing things to level up.

Poking around on TV Tropes and Wikipedia, I'm seeing suggestions that the earliest grindable games was possibly WIZARDRY, in 1981. BARD'S TALE in 1985 and HERO'S QUEST/QUEST FOR GLORY in 1989 would be other early examples. But the roguelike games might be even a couple years earlier.

Can anyone think of anything earlier for grindability?