swesor- / Indo-European roots
Sister.Perhaps originally a compound of s(w)e- and *esōr, woman, so literally "woman of one's own kin group" in an exogamous society.
1. Zero-grade form *swesr-.
a. sister from Old English sweostor, sister, and Old Norse systir, sister, both from Germanic *swestr-;
b. suffixed form *swesr-īno-. cousin from Latin sobrīnus, maternal cousin.
2. sororal, sorority; sororicide from Latin soror, sister.
[Pokorny su̯esor- 1051.]