Definition of buff:
from the skin of buffalo
or similar animals; a tool, often one covered with buff leather, used for polishing
"he's a history buff."
of the color of buff leather, a brownish yellow; unusually muscular. (also buffed)
to polish and make shiny; (computer and video games) To make a character stronger
"the enchanter buffed the paladin to prepare him to fight the dragon."
big Ugly Fat Fellow (or Fucker) The US Airforce nickname for the B-52 bomber