Why was China historically called Cathay, and who were the Tungusic rulers?

I have read history again.

then China is ruled by Tungusic peoples in the final dynasty. Now they are russian.

but they fought in an important war in middle east after china get them out.

they are basically turk? and then hairstyle like japanese too.

Why was China historically called Cathay, and who were the Tungusic rulers?
Why was China historically called Cathay, and who were the Tungusic rulers?
Why was China historically called Cathay, and who were the Tungusic rulers?
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