From Easton's 1897 Bible Dictionary :
Anah speech. (1.) One of the sons of Seir, and head of an Idumean tribe, called a Horite, as in course of time all the branches of this tribe were called from their dwelling in caves in Mount Seir (Gen. 36:20, 29; 1 Chr. 1:38). (2.) One of the two sons of Zibeon the Horite, and father of Esau's wife Aholibamah (Gen. 36:18, 24).