What is the origin/history of "you do you" (or "do you")?

The full phrase this originated from is "do you and I'll do me". Another variation is "do you - cuz I'mma do me". The oldest reference to the phrase that I could find is from the song Do You by Funkmaster Flex (featuring DMX), from the album Volume IV, released on December 5, 2000.

This could be a variation of the phrase "do your thing", which has been in use for at least a century.

1818 Frankenstein ( Mary Shelly) Chapter 19 excerpt.

Do you,’ said I, ‘enjoy yourself, and let this be our rendezvous. I may be absent a month or two; but do not interfere with my motions, I entreat you; leave me to peace and solitude.

That saying is at least 200 years old! Just stumbled on this post after listening to the read of this.

Earliest quotable reference that I know first hand comes from a song by Giant Robot and Hosni from 2004, here is the quote: "let's just say I do me, you do you, the difference is I know just what to do" - a certain degree of irony that can be detected here indicates that the phrase must have existed for some time already prior to 2004.

Sean Ryder, 1995, ‘In the name of the father’ (by Black Grape from the album ‘It’s great when you’re straight…yeah’):

“I don't do what you do And you don't do what I do But you should do…you”