So as is so often the case, it is transliteration and loaned words that seems to be at the root of this word and its variations.
Francia/frangia/fringia/ferangi.....essentially associated with quality of good steel, as with the early Frankish blades, therefore applied accordingly on trade blades.
No direct or apparant links between the words, but certainly compelling and plausible associations.
You guys are good !!!!
All the best,
Jim