dialectal possessive pronoun from your, attested from late 14c. See her.
Entries linking to yourn
your
Old English eower, possessive pronominal adjective, genitive of ge "ye" (see ye), from Proto-Germanic base of you. Cognate with Old Saxon iuwar, Old Frisian iuwer, Old Norse yðvarr, Old High German iuwer, German euer, Gothic izwar "your." Used in titles of honor by mid-14c.
her objective case
Old English hire "her," third person singular feminine dative pronoun, which replaced accusative hie beginning in 10c. See he. Cognate with Old Frisian hiri, Middle Dutch hore, Dutch haar, Old High German iru, German ihr.