| Quandary |
Well it's not EXPLICITLY stated as coming from scars (although "These savage barbarians learn to avoid blows and toughen up their skin." is close enough), but Savage Barbarian from APG gets bonus to Nat AC and Dodge AC when wearing no armor (shields OK), I'm guessing from the correlation with "no armor" that that is the one you were thinking of. Invulnerable Rager (also APG) could be similarly fluffed, granting DR instead. An explicitly scar-associated archetype is Scarred Rager (Ultimate Combat), no AC/DR but it ignores conditions and bleed, and gets Diplo/Intimidate bonus. None of those archetypes stack AFAIK.