A buff is someone with a keen interest in a subject that is not related to his or her profession.
The term was coined by New York firemen, who were often hindered by crowds who gathered at fires either to help or stand around and criticize.
At the time, around 1900, most winter coats worn by the spectators were made of buffalo hide, and from those the firemen came up with the derogatory term “buffs” to describe those pesky amateur critics.
An enthusiastic amateur is often referred to as a “buff”.
