The word "coaster" in roller coaster refers to the method of travel. Roller coaster trains are not powered. Instead they coast from one hill to the next on a set of wheels (or rollers), hence the name.
The first roller coaster was actually a coal mining car in NY in 1895 that ran 18 miles down hill and would hit a 100 MPH. People came up to the hill where it was located and road it down. Roller...