sib

The word 'sib' is a direct inheritance from Old English 'sibb', meaning "relationship, kinship, peace, friendship." This Old English term traces back to the Proto-Germanic root sibja- meaning "kin," and further to the Proto-Indo-European root s(w)e-bh(o)-, a derivative of the reflexive pronoun root s(w)e-, meaning "oneself." The core semantic link is from "self" to "one's own people," hence "kin." While largely archaic in general use, 'sib' survives in modern English as a clipped form of 'sibling' and in specialized contexts like anthropology and genetics, preserving its ancient connection to the concept of blood relation.

This is a simplex word. It is a shortening of the word 'sibling', which itself derives from Old English.