This valley branches from the valley Thrudardalur at the end of the Kollafjordur Bay and was named after the first settler, Mokollur, who built and resided at the farm Fell. Fine clay for ceramics from a mound in the valley was used for dyeing cloth and healing wounds with good results during the centuries. Some clay was transported on horses for export in the early 20th century and ideas about a railway for the purpose were never realized. The mound was declared inviolate a few years ago.
A legend tells us about a tenant farmer, who supplemented the butter used to pay the rent and the consequent proceedings. Lignite and fossilized plants and insects were also discovered in the valley.