Borrowed from Sogdian 𐼸𐼰𐼲𐼹𐼰 (kʾɣδʾ /kāγaδā/), possibly ultimately from 紙／纸 (zhǐ, “paper”).
ᠴᠠᠭᠠᠰᠤ • (čaɣasu) (Cyrillic spelling цаас (caas))
