Arabic

qafaⁿ - behind the neck, nape; back of the head, occiput (BK 2 792)

PS
*ḳapy- - occiput, back of the head (SED I No. 164)
Meanings diverse; probable semantic shift as ‘back of the head’ > ‘head’ > ‘forehead’ (S.­E.Eth.) and ‘back of the head’ > ‘back’ (MSA)