Answer
The "OM" in Sir Cyril Norman Hinshelwood OM FRS stands for the Order of Merit, a British order of chivalry established in 1902 by King Edward VII. The Order of Merit is awarded to people who have made outstanding contributions to the arts, sciences, literature, or for public service. Sir Cyril Norman Hinshelwood was awarded the Order of Merit in 1967 for his work in chemistry.