Influence of William Shakespeare on the English language
The Old English “thou” and “ye” (singular and plural respectively) were slowly substituted by Early Modern English “you”, as the difference between subject “ye” and object “you” had disappeared. By Shakespeare’s time, in the singular, it was also an alternative to “thou” and “thee” and was used as a formal way to refer to someone. Moreover, “thou” and “thee” were used by people of higher rank to refer to the ones who were above them.  “Thou” could also be used if a lower rank person wanted to refer to someone of higher rank with the purpose of disrespecting them, and Shakespeare made the most of it. For instance, he used to express that its use can be seen as a challenge: “If thou thou’st him somethrice, it shall not be amiss” (Twelfth Night)