The word 'turnstile' is a transparent compound formed from two native English elements. The first part, 'turn', originates from the Latin verb tornāre, which described the action of shaping wood on a lathe, a tool that rotates. This evolved into the general sense of rotational movement. The second part, 'stile', comes from the Old English stigel, referring to steps built into a fence to allow people to cross. The modern turnstile, patented in the 19th century, logically combines these concepts: it is a mechanical gate where one gains passage by pushing on horizontal arms that turn or rotate, replacing the function of an old-fashioned stile by controlling access rather than simply facilitating it.

Structure: turn + stile turn: From Middle English turnen, from Old English turnian and Old French torner, both from Latin tornāre ("to turn on a lathe"), from tornus ("lathe"). Functional role: Verb root indicating rotational motion. stile: From Old English stigel ("a set of steps for climbing over a fence or wall"), from a Germanic root meaning "to climb". Functional role: Noun root indicating a means of passage.