Pendulum clock is one of the first discoveries which was used as a standard timekeeping for about 270 years until the quartz clock came into charge in 1930s. A dutch physicist named Christiaan Huygnes, renowned for his studies of the Rings of the Saturn, and discovery of its moon Titan, invented the pendulum clock in 1657.
Pendulum came from a Latin word, Pendulus. It means hanging. Pendulum is a weight suspended from pivot so that it moves to and fro.
Galileo Galilei was the first person to notice that pendulums measurement was almost close to perfect for time keeping. It was his scientific investigation that made it noticeable for using pendulum as a timekeeper until 1656 when Huygens invented the pendulum clock. In the following year he patented the Pendulum clock in his name.