s/he (pron.)

Old English he, pronoun of the third person (see paradigm of Old English third person pronoun below), from Proto-Germanic *hi- (source also of Old Saxon, Old Frisian, Middle Dutch he, hi, Dutch hy, Old High German he), from PIE *ki-, variant of root *ko-, the "this, here" (as opposed to "that, there") root, and thus the source of the third person pronouns in Old English. The feminine, hio, was replaced in early Middle English by forms from other stems (see she), while the h- wore off Old English neuter hit to make modern it. The Proto-Germanic root also is the source of the first element in German heute "today," literally "the day" (compare Old English heodæg).

The paradigm in Old English was: MASCULINE SINGULAR: he (nominative), hine (accusative), his (genitive), him (dative); FEMININE SINGULAR: heo, hio (nom.), hie, hi (acc.), hire (gen. and dat.); NEUTER SINGULAR: hit (nom. and acc.), his (gen.), him (dat.); PLURAL: (all genders) hie, hi (nom. and acc.), hira, heora (gen.), him, heom (dat.).

Pleonastic use with the noun ("Mistah Kurtz, he dead") is attested from late Old English. With animal words, meaning "male" (he-goat, etc.) from c. 1300.

"the female person referred to," third person nominative fem. pronoun, used as a substitute for the name of a female or anything regarded as female, mid-12c., probably evolving from Old English seo, sio (accusative sie), fem. of the demonstrative pronoun (masc. 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 (compare 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 human being, a woman," she is attested from early 14c. Also used to signify "female" with the names of other creatures (late 14c.; she-wolf, etc.). The attempted gender-neutral pronoun form s/he is attested by 1977.