What (why, who, how, where) On Earth

Also:
(What, how, who, where) in the world
(What, how, who, where) in (God’s) creation

Meaning of Idiom ‘What On Earth’

On Earth is used as an intensifier after what (or who, where, and how) to mean in any conditions or ever. Or, when used with the word ‘where’ it means ‘in all possible places.’ The meaning of this idiom is best understood by how it is used. 1Heacock, Paul. Cambridge Dictionary of American Idioms. Cambridge: Cambridge UP, 2010. ,2Ammer, Christine. American Heritage Dictionary of Idioms. Boston: Houghton Mifflin Harcourt, 2013. ,3Jarvie, Gordon. Bloomsbury Dictionary of Idioms]. London: Bloomsbury, 2009.

Usage

This idiom and its alternatives are used in questions to express great surprise that something could ever happen or exist. 4Heacock, Paul. Cambridge Dictionary of American Idioms. Cambridge: Cambridge UP, 2010. It is often used in a negative sense. All the variations can be used as standalone phrases to express great surprise or astonishment:

“What on Earth?”
“What in the world…”

Examples Of Use

“Where on Earth did you get a copy of that book? I thought only two existed!”

“What on Earth makes you think I would ever let you borrow my car? You’ve ruined every car you’ve owned.”

“How in the world am I supposed to believe you?”

“What on in the world? Did you see how big that bird was?”

“Who on Earth do you think you are? You can’t just treat me like an underling! I don’t work for you.”

“Where in creation is that blasted phone? I’ve been looking for it all day.”

Origin

Used since the late 1700s.

More Idioms Starting with W

More Earth Idioms

More World Idioms

 

Sources   [ + ]

1, 4. Heacock, Paul. Cambridge Dictionary of American Idioms. Cambridge: Cambridge UP, 2010.
2. Ammer, Christine. American Heritage Dictionary of Idioms. Boston: Houghton Mifflin Harcourt, 2013.
3. Jarvie, Gordon. Bloomsbury Dictionary of Idioms]. London: Bloomsbury, 2009.