Officially MOAB stand for Military Ordinance Air Blast, but the name was clearly derived from Saddam Hussein's threat of the 'mother of all battles' in the 1991 Gulf War.
The bomb is a replacement for the Daisy Cutter - previously the largest conventional bomb in the US arsenal. It kills anyone within several hundred meters, and even sucks the air out of buildings and bunkers.
Saddam Hussein was fond of naming his weapons after himself. Clearly the US thought it was appropriate to indirectly name their weapons after him too.
See