Attested in Classical Mongolian as ᠰᠠᠷᠯᠤᠭ (sarlug), found also in Buryat һарлаг (harlag) and Kalmyk сарлг (sarlg).
The word is most likely a borrowing from a South Siberian Turkic language, see Tuvan сарлык (sarlık).
сарлаг • (sarlag) (Mongolian spelling ᠰᠠᠷᠯᠤᠭ (sarlug))