1 Prof. Jones: Dr Smith! Colonel Haken! Erwin! They've been...
2 Monty: Petrified. By the Gorgons' gaze.
3 Monty: Poor Ginny.
4 Minnesota Jones: I always thought she gave you a good stony stare.

"Petrified" means "turned to stone", deriving from the Greek πετρα, or petra, meaning "rock", via Latin. This is also related to the name Peter which, as anyone who has perused a baby names book will know, also means "rock".

There's another common English word with the same root: petroleum. The oleum part comes from the Latin for "oil", so the word in fact means "rock oil". Which is a fitting description for oil that comes out of the ground.

I actually learnt this particular piece of etymology from the book Asterix and the Black Gold. In this book Asterix and Obelix must travel to the lands of Arabia to find and bring back some "rock oil" for Getafix to brew the magic potion that allows the Gauls of their village to fight off the Roman army. It was obvious from the beginning that "rock oil" was essentially crude oil. When the heroes reached a supplier somewhere along their journey, he explains that the rock oil is known locally as petra-oleum.

At that point, on my first reading of the story, it was like a thunderbolt of realisation. There was a connection here that was obvious once it was pointed out, but that I'd just never mentally made myself before that time. I love these little flashes where a connection gets made between two previously unassociated bits of knowledge in your brain.