Fervor is really just an intense passion heating up. Thus we shouldn’t be surprised that it comes from the Latin root fervere (“to boil”), from which we get the Spanish for the same (“to boil”), hervir.
The seemingly unrelated words are connected through the common transformation of Latin words beginning with an f- into an h- in Spanish, such as fig and higo, and fable and hablar.
Thus, the f‑r-v of fervor maps to the h‑r-v of hervir.
The Spanish hambre, for “hunger”, makes sense if you know two different patterns.
Firstly, the initial f‑to‑h pattern: words that began with an f- then a vowel in Latin tended to have the f- turned into an h- when Spanish evolved into Latin. Huir and Fugitive is another example of that pattern.
Secondly, the mn-to-mbr pattern: when the letters in Latin “m” and “n” appear together, often separated by a vowel, they usually became “mbr” as a unit in Spanish.
Thus the f‑m-n of famine maps directly to the h‑m-b‑r of hambre.
The Spanish for “beautiful”, hermosa, seems unrelated to the English for the same. Or is it?
Hermosa comes from the Latin for “beautiful” formosus.
We can see this pattern because it is an example of the Initial F to H pattern, where many Latin words that began with F- turned into H- in Spanish.
Ahhh, that makes sense: Formosa, in Argentina really means, “Beautiful”, and this also explains the Portuguese for beautiful (also formosa) as well: Portuguese never lost that initial F.
The Latin formosus itself comes from the root forma, meaning, well, “form”. So, beauty, itself, is just your pure form. At least in Spanish.
Hierro is just Spanish for “iron”.
Here’s where it gets interesting: the Latin words beginning with f- generally turned into the silent h- in Spanish but not in the other Romantic languages, and thus hierro (from the Latin ferrum) is related to:
The Spanish for “son”, hijo, doesn’t sound like anything in English. But it is a close cousin of the English synonym for brotherliness: filial.
Both come from the Latin for “son,” filius. The transformation to Spanish came about through two interesting patterns: the initial f- in Latin usually turned into an h- in Spanish (such as, hacer and fact, or hablar and fable). The other pattern is less common: the ‑li- sound turned into a ‑j- sound — it’s just a less common sound! Thus the f‑li maps to h‑j almost exactly.
From the Latin filius, we get a few other English words, including: affiliate: an affiliate is, in a way, a child you rear!
From the same root we also get the English fetus, fecund and even feminine. These come, via the Latin filius, from the Proto-Indo-European root *dʰeh₁y-li-os, meaning, “sucker” — in the literal sense of, “one who sucks.” Children, indeed, are defined by their sucking their mothers; so your hijo is literally, “the one who sucks.” And, some might argue, even affiliates themselves usually do suck!