the correlative of brother (q.v.), a female in her relation to the other children born of the same parents, also one who has acquired such relationship by marriage, a sister-in-law, or by adoption. The O. Eng. word was sweostor; cf. Dutch zuster, Ger. Schwester, Goth. swistar; in M. Eng. this appears as suster; the Scandinavian form appears in Icel. systir, Swed. systor, Dan. s y stor, and this has curiously taken the place of the true English form suster. Outside Teut. are found Lat. soror for sosor, Skt. svasti; the origin is not known, but it may be related with Skt. svasti, happiness, joy. The Lat. consobrinus, which has given "cousin," is from con-sobrinus, sosbrinus, from the stein of soror, sister. As "brother" and "brethren" are used for the male members of a religious body or community, so also is "sister" for the female members; more particularly it is applied to the members of a female religious order or community, a "sisterhood," in the Roman and other churches, who are devoted to a religious life, works of charity or mercy, whether bound by irrevocable vows or not.

Bibliography Information
Chisholm, Hugh, General Editor. Entry for 'Sister'. 1911 Encyclopedia Britanica. https://www.studylight.org/encyclopedias/eng/bri/s/sister.html. 1910.

Bible Encyclopedias Sister

1911 Encyclopedia Britannica

Bible Encyclopedias
Sister