Perhaps from kuwr; lime (from being burned in a kiln) -- chalk(-stone).
see HEBREW kuwr
H1615. gir
גִּר noun [masculine] chalk, lime (perhaps Aramaic loan-word compare Frä9; Aramaic (also Biblical Aramaic) גִּיר ; Arabic is loan-word Fräl.c.) — גִר כְּאַבְנֵי מִזְבֵּחַ Isaiah 27:9.