From Proto-Mongolic *sïruxa, probably related somehow to Proto-Turkic *siaŕ.
Compare Dongxiang shoura, Daur shiroo (“grit found in cereal”), Turkish saz (“rush, reed”), Chuvash шур (šur, “bog, swamp”), Hungarian sár (“mud”) (from Turkic), Evenki сиругӣ (sirugī, “sand”).
шороо • (šoroo) (Mongolian spelling ᠰᠢᠷᠤᠢ (sirui))