I find it wild that English straight up borrowed a pronoun, 'they', from Old Norse. How often does that happen? Sure, pronouns aren't a closed class in many languages, but they definitely are in Indo-European! Are there any other Indo-European languages that have done this?
@awitchandherdog I'm pretty sure that the Romance third-person pronouns come from the Latin demonstratives – in the Western Romance languages they come from "ille" and "illa", for example. In fact iirc, PIE didn't have third-person pronouns at all, instead using demonstratives (which, being inflected for gender, became a natural source for pronouns later!)