Well, there are a few theories. One is that it’s an abbreviation of “Original Gangster”, a phrase or slang term used to refer to something or someone that was original or the first of a kind. Original Gangster became famously used back in the 1980’s and 90’s, when hip-hop based artists in Los Angeles used the term. These included Tupac, Snoop Dogg, and Ice Cube. It makes sense to name a strain with an OG prefix when it was the first of its kind to be developed, since there are many more that have been spawned out of these parentals. This makes it easy to identify the parent strains and those that were bred from it.