Goliath Constitution (5e Feat)
From D&D Wiki
As a Goliath, you have naturally tough skin, and yours is even harder than most of your race.
• Your Constitution score increases by 1, to a maximum of 20.
• You have thick, rough skin. While you are not wearing armor, your AC is 12 + your Dexterity modifier. You can wield a shield and still gain this benefit.
• When you your your Stone's Endurance trait, you may add half your Constitution modifier (rounded up) to the amount of damage reduced.