Did you know you is actually the plural and the singular is thou? My problem with any of this switching around is that since it's used by a very small minority

Did you know you is actually the plural and the singular is thou? My problem with any of this switching around is that since it's used by a very small minority in a very forced way, until it becomes mainstream in the way 'you' has become mainstream, it's confusing af. I've had multiple instances when a they was mentioned in a decision and I had to ask, " wait I thought we only had one designer on this ticket who else got added... Oh you're using singular they.. got it"