From Proto-Mongolic*šiker/*šikir. Probably transmitted via a Turkic language from Persianشکر(šakar), ultimately from Sanskritशर्करा(śárkarā, “ground or candied sugar, originally meaning grit, gravel”).
Initial ч-(č-) is irregular, but there exist parallels in other Mongolic and Turkic languages such as Middle Mongolian扯克兒(čeker), جَكَرْ(čeker) (a hapax legomenon) in Karakhanidيَنْدَنْ جَكَرْ(yandak čeker, “manna”, literally “camelthorn sugar”) or Kipchak[Arabic needed](čeker börek, literally “sugar burek”).