köken: From Latin soror, from a diminutive form or based on the model of fratello. Ultimately from Proto-Italic *swezōr, from Proto-Indo-European *swésōr.
one's big / elder sister · younger sister of the speaker's father or mother · a woman older than the speaker but younger than the speaker's parents, in relation to the speaker
köken: Inherited from Old Galician-Portuguese irmãa, yrmãa, from Latin germāna (“sister”), from the adjective germānus (“of siblings”); more at irmão. By surface analysis, irmão + -a (forms feminine equivalents).
köken: Etymology tree Proto-Indo-European *swé Proto-Indo-European *h₁ésh₂r̥ Proto-Indo-European *su-h₁ésh₂-ōr? Proto-Indo-European *swé Proto-Indo-European *-sōr ? Proto-Indo-European *swésōr Proto-Balto-Slavic *swésō Proto-Slavic *sesra Proto-Slavic *sestra Old Czech sestra Czech sestra Inherited from Old Czech sestra, from Proto-Slavic *sestra.
köken: Probably from the older form sor, inherited from Latin soror (nominative) via loss of /-r/ and then adjustment of the final vowel to the more typically feminine -ă (or less likely through a Vulgar Latin form *sora). The plural reflects Latin sorōres. The original form sor could occasionally be found in western Transylvania in some expressions like sor cu frate.