[akhtene]

Barahir with his men saved Finrod's life in the Dagor Bragollach (the Battle of Sudden Flame).So Finrod "swore an oath of abiding friendship and aid in every need to Barahir and all his kin, and in token of his vow he gave to Barahir his ring."
It was kept by Beren, in the Second Age it was passed to the Faithful of Numenor. Later it became an heirloom of the House of Isildur and was kept in Rivendell.