The term "dynamo" comes from the Greek word *dynamis*, which means "power" or "force." A dynamo is a type of electrical generator that converts mechanical energy into electrical energy, typically in the form of direct current (DC). The name emphasizes its ability to produce power (electricity) through mechanical movement.
The term was popularized in the late 19th century, when inventors like Michael Faraday and Werner von Siemens were developing devices that could generate electricity. So, a "dynamo" essentially means a device that creates electrical power.