The accepted hypothesis for how the Moon was formed was that something the size of Mars smacked into youngish Earth and in the same way a bullet will blow it’s way out of the back of it’s target, parts of the Earth were ejected into space.
Lucky for us the Earth’s medical waste didn’t just float off. Some of the Earth’s Earthly remains were caught in Earth’s orbit and around and around it went until the Moon was formed.
The object that hit the Earth was named Theia after the Greek Moon Goddess because, I suppose , it made sense.
However I would have an object that tried to wipe the Earth out of existence a more fitting name.
I would have named it Fang.