lawman (n.)

1530s, "lawyer," from law (n.) + man (n.). Meaning "law-enforcement officer" is from 1865. Old English had lahmann "an official or declarer of the law, one acquainted with the law and qualified to declare it," a word from Old Norse. There is an Anglo-Latin lagamannus "magistrate" from early 12c., hence the proper name of Layamon, author of the "Brut."