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.
A person or thing that strongly or exactly resembles another; duplicate; dead ringer, look-alike: She's Grace Kelly's double(1543+)
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with double back
Reverse one's course, go back the way one has come. For example, The officer lost the suspect, who had doubled back on him. This term, at first put simply as to double, is used largely to describe a way of evading pursuit.
[ Late 1500s