'rev' originates as a clipped form/abbreviation of 'revolution', ultimately from Latin 'revolutio', where 're-' meant 'back' and 'volvere' meant 'to turn/roll'.

'revolutio' passed into Old French and Middle English as 'revolution', and in modern English 'revolution' was informally shortened to 'rev' (late 19th–20th century) when referring to engine revolutions.

Initially it referred to a 'turning' or 'rotation'; over time it came to mean specifically an engine's rotation (revolutions per minute) and, as a verb, to increase that rotation — later extended figuratively to mean 'to excite' or 'increase intensity'.