What is "Kiryas Tohu"?
Rashi: When [the city] is broken, it is called Kiryas Tohu. Radak - the verse calls it Kiryas Tohu at the time of breaking, based on its end. The same applies to "Afisi Al Gechalav Lechem" (44:19) and similar verses.
Malbim: Kiryah is the fortress of the city - the roofs of the houses and the walls. It was broken.
What is the meaning of "mi'Bo"?
Rashi: [It is closed] from a man entering.
Was every house closed?
Radak: The majority were closed. The same applies to "v'Chol ha'Aretz Ba'u Mitzraimah" (Bereishis 41:57). Most of the houses will be destroyed; there is no reason to enter them.
Malbim: Yes, at the time they were about to leave their homeland to the enemy's land.
