He is MAR
He is McAllisteR
Root of the verb to mar meaning to scar, impair.
Tom MAR: the one who scars, the red smiley face.
Jared Renfrew had information about Red John which he got from Orville Tanner when they shared the same jail cell.  
MAR is a possible nickname for McAllister, or Red John.  Something that people referred to him during his childhood which 
was continued into his early years of a murderer.