דברי הימים ב לד:ו פירוש: רש״י

And in the cities of Manasseh and Ephraim, etc. from those “gleanings” [survivors] who survived the sword and the captivity of Sennacherib.

with their instruments of destruction Since they were but few “gleanings,” they feared to live in the lowland and established their houses on the mountain (בְּחַרבָּתֵּיהֶם)).