Singular "they" is attested back to the 14th century. (Note that this would actually be Middle English!) It met a lot of resistance in the 19th century by vario

Singular "they" is attested back to the 14th century. (Note that this would actually be Middle English!) It met a lot of resistance in the 19th century by various prescriptive grammar books. https://en.wikipedia.org/wiki/Singular_they https://en.wikipedia.org/wiki/Singular_they https://en.wikipedia.org/wiki/Singular_they#Trend_to_prescription_of_generic_he_from_19th_century https://en.wikipedia.org/wiki/Singular_they#Trend_to_prescri... https://en.wikipedia.org/wiki/Linguistic_prescription https://en.wikipedia.org/wiki/Linguistic_prescription