Speciality shops in Spain generally have titles that end in the suffix “-ería”. For example: “panadería”, a shop that sells bread (“pan”), or “papelería”, a shop that sells paper (“papel”) products. If you want to sell something in Spain just take the name of the product, add “-ería”, get yourself a sign made and you have your own niche market. When I first saw shops labelled “Ferretería” my first instinct was to cut it straight down to the English word “ferret” and assume that ferrets were very popular pets in Spain and consequently that there were numerous speciality stores selling them. I thought this was unlikely however, and decided that perhaps it was the word for a general pet store.
When I finally got around to looking it up I discovered that a “ferretería” is a hardware store or an ironmongers (although I don’t think those really exist anymore.) It is from the Latin root “ferrum”, meaning iron (which is where we get the “Fe” symbol for iron in the Periodic Table) and, disappointingly, has nothing to do with ferrets.
Now the question is, why in English do we use a word with a Latin root meaning iron as the name of a small, furry creature?