I'm no expert here but surely aimhacking originally implied wallhacking? The alternative requires doing actual image analysis in realtime, which AFAIK has only become feasible in the last decade and is way more processor-intensive than just reading coordinates in memory and doing some trig to adjust your aim height. Maybe this is selection bias talking, but I see plenty of videos of cheaters who are obviously just snapping to heads through walls.
You don't actually need image analysis. There are tricks you can use to decide if an enemy is visible or not without it - obviously the game itself does it already to decide if it should draw the enemies to begin with :)
Also yes these were invented a long time ago because people got caught snapping through the wall when CS servers started recording demos.
Since you can check in memory where the enemies head is, you can obviously also check if theres a wall inbetween. Cheats for video games have had humanizing/cloaking forever.
