beater (n.) Look up beater at Dictionary.com
mid-14c., "an implement for beating;" mid-15c., "a person who punishes" (c.1200 as a surname); agent noun from beat (v.). Of various mechanical devices that "beat" in some sense from early 17c. Meaning "one who rouses game" is from 1825. Slang meaning "old car" is from c.1980.