From Robert Peel, who as Home Secretary founded the first organised police force in London in 1829. In fact, their nickname was originally 'Peelers', before we settled on the more fmailiar 'Bobbies'.
As mike says "peelers" was the nickname originally used here and you'll find the in Northern Ireland they are still known and called that (at least that's the nicest thing they are called) to this very day.