This is again a memory refreshing question.
I am looking for a specific kinship term that is considered to be inherited into a Scandinavian dialect despite the fact that no other Germanic language has any attestation of it. Its closest cognates are found in the Indo-iranian languages (or more specifically, Iranian, if I remember right).
I remember having read about it and a longer argument was made in favour of its inheritance, but I have forgotten both the reference where I read about it and the term itself.
I'd like to know the term which can be a handle to find more information, naming a reference for it is a clear bonus.