I was interested in learning that the term 'nerf' originated from Nerf gun toys. The opposite of nerf is buff, but I have found no information on the origin of it.
In the video game community, how did the term 'buff' originate?
The English Stack Exchange does a good job explaining the history of this word.
The word "buff" also means to polish something and make it more attractive. Keeping that in mind, when you buff a character in a video game, you're "polishing" them up, get it?
Here's anarchy online Nov 2001 with "I watched MA get buffed.. then nerfed".
Before "Buff" was the opposite of "Nerf", "Buff" was the opposite of "Debuff". I learned of the word buff in everquest(1999). Primarily the word was used to describe spells that one character would cast to enhance another. Examples are, the shaman run speed buff (SoW) or the enchanter mana regen buff (Clarity).
There are certainly older references than this - reaching into MUDs, MOOs and penAndPaper games.
Since the word was in use as a temporary improvement mechanic in games, it is sensible that it was later picked up to describe dev changes which are considered improvements.
I am not sure of the exact origins of the word "buff" as it applys to gaming. However, I can say when and where I personally heard "buff" and "nerf" used in a gaming context. I first heard about "nerf" when reading an Ultima Online forum post in the late 90s, regarding a balancing change effecting some weapons. The forum poster stated they might as well be fighting with Nerf bats.
I first heard the word "buff" while playing Everquest. There was a low level spell which would increase the strength stat. When the spell was applied, there was an icon of a big, bulging bicep on your screen. Some players said "I will buff you up" or some reference like that while casting it in the first weeks since the game's release. I am not sure why, but I just went with it. Soon the term was applied to everything which caused a stat increase, or benefit. Soon after, I heard debuff when refering to spells which lowered something's fighting stats.