The term came to fruition through Sanchez noticing how as Mexican men age, they tend to morph into the description of Tyrannosaurus Mex with larger stomachs and seemingly smaller arms.
Bobby - Yeah! And his tiny arms! He's totally a tyrannosaurus mex.
Guy 2: You Mean That Tyrannosaurus Rex?
Guy 1: No Can't You See The Sombrero?
Guy 2: Oh I see Its A Tyrannosaurus Mex