They is Norse, borrowed about 1200 from Old Norse þeir, and it displaced the native English plural pronoun entirely by about 1400. Along with them and their, it is the most extraordinary of all Norse borrowings, because pronouns sit at the very centre of a language's grammar and are almost never taken from outside.
The reason it happened is legible. The native Old English plurals were hi and hie, and centuries of sound change had worn them dangerously close to he, heo and hit — he, she and it. The Norse forms began with th-, which slotted neatly beside the, that and this, and were simply easier to tell apart. As one historian of the language put it, they entered readily into the system of English pronouns and were felt to be more distinct than the native forms they supplanted. Practical convenience beat a thousand years of inheritance.
they (pron.) nominative case pronoun of the third person plural, "persons or things in question or last mentioned," c. 1200, from a Scandinavian source (Old Norse þeir , Old Danish þer , þair ), originally a masculine plural demonstrative pronoun. By c. 1400 it had displaced Middle English he , hei , from Old English hi , hie , plurals of he , heo "she," hit "it." The most important importation of this kind [from Scandinavian to English] was that of the pronomial forms they , them and their , which entered readily into the system of English pronouns beginning with the same sound ( the , that , this ) and were felt to be more distinct than the old native forms which they supplanted. Indeed these were liable to constant confusion with some forms of the singular number ( he , him , her ) after the vowels has become obscured, so that he and hie , him and heom , her ( hire ) and heora could no longer be kept easily apart. [Jespersen, "Growth and Structure of the English Language"] The Scandinavian source of they is from Proto-Germanic *thai , nominative plural pronoun, from PIE *to- , demonstrative pronoun (see that ). From c. 1400 as "people in general." Colloquial use of they for "anonymous people in authority" is attested from 1886. They say for "it is said" is in Milton. With reference to singular nouns by 1520s, especially with words in every , any , etc. [Y]ou desire to be just and honest and to give every Body their due .... [William Notcott, "Jesus Christ Most Precious to Every True Believer," 1735] also from c. 1200
they came in through Old Norse, and its spelling follows that family's conventions.
What gives it away on the page
| core vocabulary that isn't Old English | Borrowing pronouns is rare and marks deep contact, not fashion.they, them, their, are, take, want, die, knife, window, law |
Old Norse in the spelling guide · guess another word's family