The word "her" is a pronoun used to refer to a female or a person who identifies as female. It is typically used to indicate possession (her book, her ideas) or as the object of a verb or preposition (I saw her, I gave her the book).
The word "her" originates from Middle English "hir," which comes from Old English "hire." It has been used to denote female possession or reference since at least the early medieval period.