ARBA is named 'the father of the Anak' in Jos 14:15 (so read also Jos 21:11, cf. Jos 15:13). This means simply that he was the founder of the city which bore his name; that is Kiriath-arba, later Hebron (wh. see), where was a chief seat of the Anakim.
J. F. McCurdy.
And the name of Hebron formerly [was] Kiriath Arba; [Arba was] the greatest person among the Anakites. And the land rested from war.
{According to the commandment of Yahweh to Joshua}, he gave to Caleb son of Jephunneh a plot of ground among the descendants of Judah, Kiriath Arba, which [is] Hebron ([Arba] was Anak's father).
And they gave to them Kiriath Arba, [Arba being] the father of Anak (that [is], Hebron), in the hill country of Judah and the pasturelands surrounding it.