Boyd’s Bible Dictionary:
(collected). That part of Jerusalem north of the old city (2 Kings 22:14).
Concise Bible Dictionary:
The Hebrew word signifies “second part,” as in the margin of 2 Kings 22:14 and 2 Chronicles 34:22. It may refer to a part of the city where there was a school. The Rabbis derive it from “to teach”; hence “the school” of the prophets.