Wrapped bread. That was actually the original advertisement campaign for the sliced bread people: "The greatest thing since wrapped bread" or something like that.
Sliced bread doesn't really refer to a slice of bread. It refers to bread that comes pre-sliced in a package, which came about in the late 1920s. But, before that, people had to invent a package that could keep bread from going stale, even when it is sliced.