What is the meaning of Nerf?

To bump lightly, whether accidentally or purposefully.

To change a mechanic, an ability or a character in a video game in order to make a previously dominant strategy less viable or less effective.

To arbitrarily limit or reduce the capability of.

The deterioration, weakening or worsening of a character, a weapon, a spell, etc.

grain of wood

a similar line in leather, paper, etc.

nerve

vein of a leaf

nerve

force, power, strength

nerve

nerve

nerf (worsening of a game mechanic)

nerve

Source: wiktionary.org