Possibly means ‘Sea-crowned’? ‘aer’ = sea and ‘rîn’ = crowned

Aerin was a kinswoman of Húrin in Dor-lómin. When the Easterlings came into Hithlum they did much evil there. They despised the remnant of the people of Hador and they stole from them and enslaved their children. Aerin was taken as wife by Brodda the Easterling.

It was Aerin who aided Morwen, the wife of Húrin, and the mother of Túrin and Nienor, after the Nirnaeth Arnoediad because Morwen was left poor and without any aid. When finally Turin came looking for his mother and sister, it was Aerin who told him where they had gone.
Encyclopedia entry originally written by Nienna-of-the-Valar