Sestar

Etymology
From Proto-Indo-European *sestar (sister).

It has 4 meanings:
 * A female sibling.
 * A female having parents in common.
 * A female fellow member of a religious community.
 * Colloquially, a nun.

Derived words

 * alsestar (n), sister-in-law.
 * kisestar (n), step-sister.
 * sesmata (n), aunt.