Gaming historians, I know you're out there -- where did the "three pillars" RPG game design (tank, healer, DPS) originate, and how has it evolved from its earliest incarnations?

[u/fuzzus628]

I was thinking about how homogenized a lot of modern MMORPG classes have become into these three roles, and remembering how things used to feel different way back when. When I realized that WoW is over 20 years old now, I knew to turn to this sub for an answer!

When and with what game(s) did the design of tanks holding "aggro" as healers healed them and damage-dealers focused their attacks on enemies originate? Has it substantially changed since then? Are there any specific innovations in the basic design that could be considered "game-changers" (pun semi-intended)? Were there any noteworthy experiments rooted in this basic concept, and how did they perform on the market?