Forest of Region
The Forest of Region was the forest, primarily made up of holly, within which lay the halls of Menegroth. Region formed the southern and greater part of the Kingdom of Doriath. It was bounded by the rivers Aros and Esgalduin, and the Girdle of Melian.
Region is Doriathrin. It is a genetive plural of reg, "holly tree". The name thus means "(Land) of Hollies". Compare Eregion.
Region is pronounced "reg-ion" because it is an Elvish name, not "region" as in "a region of land".