early 13c., from O.Fr. duble, from L. duplus "twofold," from duo "two" + -plus "fold." Verb meaning "to work as, in addition to one's regular job" is c.1920, circus slang, from performers who also played in the band. Double-header is first recorded 1869, Amer.Eng., originally a kind of fireworks or a railway train pulled by two engines; baseball sense is c.1890. Double Dutch "gibberish" is attested from 1864 (High Dutch for "incomprehensible language" is recorded from 1789). Double agent is first attested 1935; double date is from 1931. Double-take and double talk both first attested 1938. Military double time (1833) was originally 130 steps per minute; in modern U.S. Army 180 steps of 36 inches in a minute. To double park a motor vehicle is recorded from 1931.