“Anakim.” The Anakim were descendants of Anak, who was one of the Nephilim, as Numbers 13:33 says.
[For more on the Nephilim, see commentary on Gen. 6:4.]
“all the hill country of Judah and from all the hill country of Israel.” The division of Israel and Judah could easily come from the fact that Joshua fought his first battles in or close to Judah, and knew he would have to conquer the land given to the rest of Israel after that. It is possible but less likely that a later editor added the distinction for clarity.
“devoted them to destruction.” For more on things “devoted” to Yahweh and devoted to destruction, see commentary on Josh. 6:17.
“Joshua came at that time, and cut off the Anakim from...Hebron.” This attack is recorded in Judges 1:10.