“Fierro” is the same as saying “let's do it” or “sounds good” or “you got it!”. It's usually used when dismissing each other, or setting up a meeting of some sort. The true meaning is “iron” or “metal” but it's not used literally.
"1. handsome ugly old little 2. dark under unfriendly blond 3. tall slim under ugly 4. fat slim unfriendly blond 5. young bad little old 6. big blond little brown 7. nice big unfriendly old."
