Such a simple word like sheriff hardly seems like it would elicit a convoluted origin. However, it is rather complicated. Somewhere between Old English and Middle English, the word evolved from the previous word scirgerefa, which literally meant "local official in a shire", as a combination of scir ("shire") and gerefa ("officer"). Scir, now, came from the Proto-Germanic word skiro, meaning "district", which derives from the Proto-Indo-European word for "to cut" (since districts were divided, or "cut"), ker. Meanwhile, gerefa was developing from the Germanic family of languages, but we're not exactly sure what it was before; only that it had vague military connotations. It seems to possibly be a portmanteau of the intensifier ge and the root rof", which may have meant "host" in the archaic form (like a battalion, almost). Meh. What we know for sure is that sheriff used to mean something like "army cutter".
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
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