Etymology tree
Proto-Indo-European *ḱorkeh₂
Proto-Indo-Iranian *ćárkaraH
Proto-Indo-Aryan *śárkaraH
Sanskrit शर्करा (śárkarā)
Gandhari 𐨭𐨐𐨪 (śakara)bor.
Middle Persian 𐭱𐭪𐭥 (šakar)bor.
Arabic سكر
Borrowed from Middle Persian 𐭱𐭪𐭥 (šakar), borrowed from Gandhari 𐨭𐨐𐨪 (śakara), from Sanskrit शर्करा (śárkarā), from Proto-Indo-Aryan *śárkaraH, from Proto-Indo-Iranian *ćárkaraH, from Proto-Indo-European *ḱorkeh₂ (“gravel”).
For the vocalism from Middle Persian to Arabic, compare أُشَّق (ʔuššaq, “ammoniacum”).