About
Mah Nigga is a reaction image used to express agreement with someone.
Origin
The phrase originates from the 2001 film, Training Day. The film is about two LAPD narcotics detectives who enforce the law in the ganglands of Los Angeles. At one point in the film, Denzel Washington’s character and Ethan Hawke’s character are in a car, and are having a conversation about something. During the conversation, Washington’s character says to Hawke’s character, “Mah Nigga,” and puts what appears to be a marijuana joint in his mouth.
Spread
It is unknown where the meme first began to take off, however, according to Google Insights, the meme first surfaced around February 2012.