Up the / out the "ying yang"

Factual Questions
1

Where did the phrases “up the ying yang” and “out the ying yang” come from? Anyone?

2

I think it was the same place where “out the wazoo” came from.

3

I’d have to google to find out waht a wazoo is, but of course a ying yang is a design made by placing two equal circles inside a larger circle to exactly fill it, then dividing them with the “S” shape they make into two hemispheres.

Used in the OP’s context because of its resemblance (somewhat) to an anal fistula.