Hi,
This sounds a bit like asking the origin of an everyday modern phrase like 'Where are you?'
However, OK, I'll try again. Here are a couple of interesting quotations, although I wouldn't claim that either is the origin of the phrase.
This is from the King James version of the Bible (Genesis, Chapter 3).
9 And the LORD God called unto Adam, and said unto him, Where art thou?
10 And he said, I heard thy voice in the garden, and I was afraid, because I was naked; and I hid myself.
However, please note that English was not God's first language.
The above is a translation.
Here is a sonnet by Shakespeare.
Where art thou, Muse, that thou forget'st so long
To speak of that which gives thee all thy might?
Spend'st thou thy fury on some worthless song,
Darkening thy power to lend base subjects light?
Return, forgetful Muse, and straight redeem
In gentle numbers time so idly spent;
Sing to the ear that doth thy lays esteem,
And gives thy pen both skill and argument.
Rise, resty Muse, my love's sweet face survey
If time have any wrinkle graven there;
If any, be a satire to decay,
And make time's spoils despisèd everywhere.
Give my love fame faster than Time wastes life;
So thou prevent'st his scythe and crooked knife.
Best wishes, Clive