What is "ferro-"

Ferro- \Fer"ro-\ (Chem.) A prefix, or combining form, indicating ferrous iron as an ingredient; as, ferrocyanide.

before vowels ferr-, word-forming element indicating the presence of or derivation from iron, from Latin ferro-, comb. form of ferrum "iron," which is of unknown origin. Possibly of Semitic origin, via Etruscan [Klein]; Watkins suggests "possibly borrowed (via Etruscan) from the same obscure source as OE bræs "brass." Also sometimes especially indicative of the presence of iron in the ferrous state; ferri- indicating iron in the ferric state.

pre. 1 iron (''the element''); pertaining to iron 2 (context chemistry English) ferrous