'rev' is a shortening of 'revolution' in the context of engines, where 'revolution' refers to a complete turn or cycle.

'revolution' was commonly used in the 19th and 20th centuries to describe engine cycles, and 'rev' emerged as a clipped form in the early 20th century, especially in automotive contexts.

Initially, 'rev' referred specifically to engine revolutions, but it later gained figurative meanings related to increasing energy or excitement.