Why is Chapter 5 called Maus Holes?

Part of this chapter chronicles the attempts by Jews to hide from the Nazis in small spaces (hence the title.) In Srodula, the Germans begin to round up Jews at random. To protect himself and his family, Vladek builds a shelter under a coal bin, in which they hide during Nazi searches. Soon, though, they are moved to a different house. Again, Vladek builds a shelter, this time in the attic and accessible only through a chandelier in the ceiling.