Forodwaith was the name both of a region and the people that lived there.
The Sindarin name Forodwaith translates loosely as Northern Waste, and was a name for the land north of the Iron Mountains of the First Age. Little was known of it, except that it was an area of immense cold due to the proximity to the Gap of Ilmen, and Morgoth's evil cold.
After the War of Wrath and the breaking of the World, the Iron Mountains were mostly destroyed, and the area of Forodwaith that lay north of Eriador became known as Forochel, together with the great ice-bay and -cape that carried the same name.
The Men of Forodwaith were a strange folk apparently unrelated to the Edain. During the Third Age they were known as the Snowmen of Forochel or Lossoth. In Unfinished Tales it was stated that they could glide on ice by tying bones to their feet.
Arvedui, last King of Arthedain, fled to the Ice-bay of Forochel after his realm was destroyed by Angmar, and the Lossoth helped him survive the winter. Against their advice he took ship to sail south, and he was drowned in the ice-bay, together with the Palantíri of the North.