In the manga Otoyomegatari, there exists a concept of sisterhood bonding called xwahar xande in 19th century Iran and Central Asia. Does this practice actually exists or is based on an actual historical practice?

by Zooasaurus

Specifically, two women swore to "never dislike each other, to never speak ill of each other, and that they will be nothing but the best of friends" under a witness

mirshafie

I can't answer your question, and you might already know this, but for what it's worth "xwahar xande" is Farsi. It means "sister of laughter". It could also be "xwahar xaande" which would mean "sister of learning".