Cogwheel is a compound of cog (Middle English cogge 'tooth on a wheel', probably of Scandinavian origin) + wheel. Morphologically, cogwheel is transparent: it is a compound of cog (Middle English cogge 'tooth on a wheel', probably of Scandinavian origin) + wheel. Used as a noun, cogwheel now means "a wheel with teeth on its rim that meshes with another to transmit motion", so the present definition can be read against the older forms and meanings. The same lexical family is also visible in related forms such as cog and wheel. The modern word remains analyzable through its parts, which makes the semantic connection unusually direct.