Etymology of "[Where/What/Why] in the world" idiom? [closed]

I've searched the internet and found definitions, but I cannot figure out when this would have EVER meant anything. Any ideas? Specifically, the type of phrase I am referring to is "What in the world were you thinking?" or "Why in the world would I want to do that?" In those questions, "in the world" is used to emphasize how ridiculous the OP must have been when making such a decision.

What in the world were you thinking? is a rhetorical question. That means it is actually a statement:

In this world (in actual reality) there is nothing that could explain you thoughts.

Similarly, why in the world would I do that? is rhetorical for:

In this world there is no reason why I would do that.

So basically, adding in the world to a rhetorical question implies that what the person was doing, thinking, saying or asking is not in the realm of this world: it is out of this world, it is unrealistic, it is absurd.

This is one of those expressions that is so old that it is almost literally translated from Latin, as in "Nulla in mundo pax sincera" ("In this world there is no honest peace.") which is based on an anonymous, ancient poem. The sense of "in the world" being a synonym for "to exist" is found in the Roman legal proverb: "Quod non est in actis, non est in mundo:" "That which is not in the statutes is not in the world."

A similar idiom is "It's Greek to me," which comes from the Latin via Shakespeare.

According to Ngram the expressions ( What/Why in the world) have been used for at least the last two centuries. The earliest instance I could find dates back to 1733:

This seems so fair, so exact, that what in the World could have a better Face? Yet for all this, the Scots do not fail to complain of him, and affirm that he had regard only to his own Interests. Therefore to have a clear and distinct Idea of this Affair, 'tis worth while to look into the Complaints of the Scots, and to see on what they are founded, tho this is what Mr. Rymer's Collection takes no notice of.

I don't think they have a specific etymology but they are just a way to give emphasis to what one is saying.!