To police is to maintain law and order, but the word derives from polis—the Greek for “city,” or “polity”—by way of politia, the Latin for “citizenship,” and it entered English from the Middle French police, which meant not constables but government. “The police,” as a civil force charged with deterring crime, came to the United States from England and is generally associated with monarchy—“keeping the king’s peace”—which makes it surprising that, in the antimonarchical United States, it got so big, so fast. The reason is, mainly, slavery.
Read more at the New Yorker.