Akkadian

ḳuddušu - to make ritually clean, to purify (CAD Q 46; AHw. 891)

cf. ḳašdu ‘holy’ (CAD Q 146; AHw. 906); ḳadištu ‘a woman of special status’ (CAD Q 48; AHw. 891)

PS
*ḳdš - sacred (HALOT 1066)