I was trying to think on the history of this feature, since i wouldn’t necessarily count something like AvP’s heatvision mode. That’s meant to simulate a real thing, even if it works a bit gamey, by highlighting active objects.

Assassin’s Creed is the game that, for me, codified the mechanic into it’s current form. Hawk Vision or whatever they called it specifically highlighted game objects. I think they even mention that the animus machine is projecting that view to help Desmond see the world how his ancestors would have understood it.

But… I’m going to call the origin as being way farther back. In flight sims, your targeting hud can highlight enemies and targets by drawing little boxes around them. That is the very first instance I can think of where a game highlighted objects of interest for the player’s benefit. Most flight sims (or adjacent genres like mech sims) would also label the box with the name of the thing, sometimes with health, ammo, weapon, or weakpoint indicators as well.