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a Hebrew word always used with the article, “the” Millo
This was the name of two Biblical places.
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 defense
It is always rendered Akra i.e., “the citadel”, in the LXX. It was already existing when David conquered Jerusalem (2 Samuel 5:9). He extended it to the right and left, thus completing the defense of the city.
It was rebuilt by Solomon (1 Kings 9:15, 24; 11:27) and repaired by Hezekiah (2 Chronicles 32:5).
In Judges 9:6, 20 it is the name of a rampart in Shechem, probably the “tower of Shechem” (9:46, 49).