You can read a little about Crapper here.
The slang term came from his name, not the other way around.
The "flushing" toilet has been around a lot longer though. I well remember a toilet building in the Minoan palace Knossos on the Greek island Crete has a working "flushing" toilet, the palace is 3,500 years old. The toilet is a small room with a stone seat with a hole in it, the "waste products" fall through a larger hole in the stone floor into a trough where a continuous stream of water is running to carry the unwanted material out of the palace and into a large septic tank from which agricultural fertilizer was made.
