Edom in Fausset's Bible Dictionary

Idumea. ("red".) Esau's surname, the firstborn of Isaac; Jacob's twin brother, who sold his birthright for the red pottage (of yellow brown lentils, dashim; the cooking of which is still seen in Egyptian representations), from whence came his surname (Genesis 25:29-34). The name was appropriate to Edom's possession, "mount Seir," the mountainous territory having a reddish hue. Seir means rugged, applicable alike to Seir the hirsute (like Esau) progenitor of the Horites, Edom's predecessors, and to their rugged forest covered territory (Genesis 14:6; Genesis 32:3; Genesis 36:1-8; Genesis 36:20- 22). It extended from the Dead Sea S. to the Elanitic gulf of the Red Sea. Esau, with his 400 armed men (Genesis 32:6), commenced driving out the Horites, and permanently settled in mount Seir after his father's death, yielding Canaan to Jacob, in accordance with his father's blessing...