Etymology

Nerf brand toys are made of soft foam and are ineffective as actual weapons. One can hypothesize that the term "to nerf", in the context of gaming, came about from explaining that a particular in-game weapon or strategy had been rendered ineffective by whichever party that controls and maintains the game.

Verb

1. To bump lightly, whether accidentally or purposefully.

   A racer will often nerf another as a psychological tactic.

2. to water down, dumb down or especially weaken. (A term derived from the foam brand of toys, which are generally made safe for play.)

   The lightning spell was pretty powerful before they nerfed it.