Does "marriage" exist, as a "natural, inarguable phenomena" independent of its social construct?

What about "US citizen"?

I don't think so.

Which means we can't say the existence of a word means its the result of a physical assumption.

When you wrote "planets, stars", did you not assume those two are different? But originally, "planet" meant "wandering star" - a planet was assumed to be a type of star.