early 15c., "spiked road barrier used for defense," from turn + pike (n.2) "shaft." Sense transferred to "horizontal cross of timber, turning on a vertical pin" (1540s), which were used to bar horses from foot roads. This led to the sense of "barrier to stop passage until a toll is paid" (1670s). Meaning "road with a toll gate" is from 1748, shortening of turnpike road (1745).
updated on August 16, 2012