The pronoun ‘they’ was borrowed into English from Old Norse. Pronouns within a language tend to be conservative over time, so this borrowing of a foreign pronoun into English is a bit unusual. In today's episode, we explore the entire history of "they," from its roots as a Proto-Germanic demonstrative adjective to its modern usage as a singular, gender-neutral pronoun in English.

Subjectification is a unique linguistic process by which a word evolves to reflect the subjective viewpoint of the speaker using it. For example, the word ‘very’ used to mean ‘true,’ but over time, it lost its objectivity and merely became a way of emphasizing subjectivity. In this episode, we explore this process in a broad sense and look at a few more examples. 

Further reading:

https://web.stanford.edu/~traugott/resources/TraugottDavidseIntersbfn.pdf

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1028.5275&rep=rep1&type=pdf