Millo

"(Heb. always with the article, "the" Millo). (1.) Probably the" "Canaanite name of some fortification, consisting of walls filled" "in with earth and stones, which protected Jerusalem on the north" "as its outermost defence. It is always rendered Akra i.e., "the" "citadel", in the LXX. It was already existing when David" conquered Jerusalem (2 Sam. 5:9). He extended it to the right "and left, thus completing the defence of the city. It was" "rebuilt by Solomon (1 Kings 9:15, 24; 11:27) and repaired by" Hezekiah (2 Chr. 32:5). "(2.) In Judg. 9:6, 20 it is the name of a rampart in Shechem, "probably the "tower of Shechem" (9:46, 49)."

Definition of Millo:
"fullness"