Spanish Omelette-Need help!

[DreamsLikeACat]

Ok, so I'm makeing a spanish omelette for my spanish class and I need some help.
1) Is it's origin from Spain?

2) Please help me translate these ingredients into proper spanish:
6-7 medium potatoes, peeled
1 whole yellow onion
5-6 large eggs
2-3 cups of olive oil for pan frying
Salt to taste

3)If you can tell some history on it, that'd be great!