Engine The word “engine” comes from the Latin word “ingenue.” An engine is a device or system (electrical, mechanical, chemical, or even social, human, or political) which affects a result. For instance, a bomb is an engine, a crane is an engine, a water-powered mill is an engine, a political party is also an engine, and even a criminal gang is an engine. Gradually through the decades, “engine” became associated especially with boilers, fire, furnaces, and bombs. In short, any device which tended to get hot and explode. However, the system was still considered to be an “engine” and not just the prime mover. In the 20th century, a motor prime mover was called “the engine.” James Watt put the name “steam” in front of the engine to distinguish it from other engines of that time. Engines are basically the devices which convert any form of energy to bring about mechanical effects. These are made up of pistons and cylinders. These may be categorized into various groups according to