This didn't unlock when I equipped two random rings. It only unlocked when I equipped two rings of the same rarity - in my case, I equipped 2x Green (Uncommon) Rings, and it popped. It should work with 2x Blue and 2x Orange Rings as well, just now 2 rings with different colors.
Just sharing in case you're having issues with this. The unlocking of achievements has been quite dodgy for me for this game.