I'm an engineer but I've never designed a motor. The classical definition of engine was a complex piece of machinery or instrument, like a siege engine, and doesn't necessarily imply a power output.
Modern day engines versus motors- engines convert fuel (chemical energy) into another form to produce motion. Motors do not change the form of the fuel, only the potential energy. For instance, steam turbines and air motors take heat or pressure out of the steam/air to make motion, but do not change it chemically. Electric motors form a resistance to electrical current to create motion, but they do not alter the electrons as they pass through the motor. The energy to power a motor comes from somewhere outside the motor, but an engine generates its own power by converting chemicals into energy.
