This phrase has it`s origins with the Call Of Duty Commentator Thunder Toro (aka TheLEDGENDOFTHUNDER and 4022THUNDER402). In a commentary , whistle being attacked by the no-scoping beast, Ravenous
Randy (aka zzirrandy), Thunder survived and killed
randy and bellowed "YOU AIN`T GIZZ BABY" referring legendary Call Of Duty sniper zzirrgrizz (because
randy failed to no-scope thunder, he was not grizz). Since then, the phrase has spread throughout the video game community, being picked up by
people like Hutch and Goldglove, who named their podcast "you ain`t grizz baby". zzirgrizz himself has since commented on the issue saying he thinks that it is
funny. The phrase begun to be used whenever a sniper in general has been killed.