PS

*ḳVdḳVd- - skull (SED I No. 159)

Akkadian
ḳaḳḳadu - head (CAD Q 100, AHw. 899)
Ebla
gag-gú-tum /ḳaḳḳudum/ - = Sum. SAGxIGI (VE 267, Krebernik 1983: 12)
Ugaritic
ḳdḳd - skull, crown (DUL 694)
Hebrew
ḳodḳōd - skull (HALOT 1071)
Jewish Palestinian Aramaic
ḳwdḳd - head, skull (DJPA 478)
Samaritan
ḳdḳd - head, leader (DSA 758)
Jewish Babylonian Aramaic
ḳodḳədā - head, skull, vertex (Jastrow 1317)
Jewish Babylonian Aramaic
ḳwdḳdˀ - skull (DJBA 989)
Mlaḥso
kotke - skull (J Mlaḥ. 180])
Problematic. Can it be eventually from *ḳVdḳVd-?
Arabic
maqadd-, muqadd­- - part of the back of the neck that is between the ears (BK 2 683, Lane 2492)
Harari
ēḳäd - front, forward, chief, head (EDH 30)
<*ˀV-ḳad, with a prefixed element