We've been accustomed to the concept of privilege for as long as the English language existed. There are attestations from the dark ages of it being used as a Latin word in an English context, but it really started to grow its own identity in the 1100s CE. Since those early days, the Oxford English dictionaries lists 131 different forms of the word emerging, with spellings as diverse as priuilag and prewyllage; by the eighteenth century privilege was pretty standardized, especially due to influence from the French cognate. The aforementioned Latin word was privilegium, which had the very specific definition of "law applying to one person". That's composed of the roots privus, meaning "individual", lex, meaning "law", and the noun-forming suffix -ium. Privus (the etymon of private) comes from the Proto-Indo-European reconstruction per, or "forward", and lex comes from PIE leg, "to gather".
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.