The title, like that of the preceding album On the Waters, is a Biblical pun on the name Bread, in this case the manna from Heaven which was fed to the Israelites. Although it was not literally bread (the word "manna" simply means "What is it?")
The title of the album, like its predecessor "On the Waters," uses a biblical pun on the name Bread, referencing the manna given to the Israelites in the Bible.  Although it wasn't literal bread ("Manna" just means "what is it?"), the title plays on this concept.