Quiz: Remember the definition of mal de mer?
mid-12c., probably evolving from Old English seo, sio (accusative sie), fem. of demonstrative pronoun se "the," from PIE root *so- "this, that" (see the). The Old English word for "she" was heo, hio, however by 13c. the pronunciation of this had converged by phonetic evolution with he "he," which apparently led to the fem. demonstrative pronoun being used in place of the pronoun (cf. similar development in Dutch zij, German sie, Greek he, etc.). The original h- survives in her. A relic of the Old English pronoun is in Manchester-area dialectal oo "she." As a noun meaning "a female," she is attested from 1530s.