Sibling terminology in Homer: problems with κασίγνητος and ἀδελφεός

Homeric Greek has two sibling terms: (1) κασίγνητος, a general term for any sibling; (2) ἀδελφεός, a male ego’s male sibling. Existing scholarship has tried to draw various kinds of distinctions between the two terms, mostly linguistic. The restriction of ἀδελφεός to male ego -- a new observation -- poses anthropological problems, but the solution proposed here is once again linguistic. In a nutshell, my solution is based on Perpillou's argument that ἀδελφεός is a relic of a lost collocation *φράτηρ ἀδελφεός "uterine brother", which must have dropped out of hexameter in the early Dark Age when it became metrically intolerable. Other issues in the relationship between the two terms are to be explained by the fact that ἀδελφεός is an archaism, and not a neologism as one might think.