A lot of modern misunderstanding in this article. Thou and you are exactly the same, but confusion arose during the transition from Anglo Saxon and Norman French script to modern English.
Anglo Saxon had a letter 'Thorn' signifying the 'th; sound.
Thorn could be written several ways and one of the later versions looks like a modern 'Y' but with curved arms Some examples are given in this Wikipedia article: https://en.wikipedia.org/wiki/Thorn_(letter)#Middle_and_Early_Modern_English
So the Anglo Saxon 'thou' would have looked to a French speaker like You, with 'thorn' being mistaken for 'igreque' (French)