Soqotri

dédo - 1. paternal uncle; 2. father-in-law (LS 123, CSOL I 525, CSOL II 443)

di-dédo ‘nephew’ as in wa-yaˁámer heʸ díˀʸhe dédo tóˀo ˁö́ḳar ḥóuton ɛ di-dédo ‘When he grew up, his uncle said to him: “You should be circumcised, my nephew!”’ (CSOL I 28:8)

PS
*dād- - paternal uncle (Kogan 2014: 93)
An eventual relationship with Akk. dādu ‘love-making; object of love, darling, favorite’, Hbr. dōd ‘beloved; love’ is also conceivable