"The Rolls-Royce Merlin is a British liquid-cooled, V-12, piston aero engine, of 27-litre (1,650 cu in) capacity. Rolls-Royce Limited designed and built the engine as a private venture. Initially known as the PV-12, it was later called Merlin following the company convention of naming its piston aero engines after birds of prey.The PV-12 first ran in 1933 and, after several modifications, the first production variants were built in 1936."@en .