Otoño doesn’t sound much like its English translation, fall (the season). But if we think of the less common synonym, Autumn, then the pattern becomes a bit clearer.
Both come from the Latin for the same, Autumnus. But Latin words with an m‑n sound usually became an ñ sound in Spanish. Think of damn and daño, for example. So the a‑t-m‑n of autumn maps to the o‑t-ñ of otoño!
The Spanish Miedo (“fear”) comes from the Latin metus, for “fear.”
From that same root, we get the English… meticulous. Meticulous literally means, “full of fear”: and who is meticulous about every tiny little detail if not the person who is full of fear of messing up?
We can see the m‑t of meticulous maps to the m‑d of miedo.
Postizo, Spanish for “false, artificial; in particular, a fake hairpiece” comes from the Latin positus, which meant, “put into its place.” If we’re wondering how “put into its place” came to mean “fake”, just think of the most common use of the Spanish word: for a wig. You put your fake hair into place!
From that same root, we also get the English posit — which is, quite literally, putting an idea into its place.
We can see the p‑s-t root clearly in both words.
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 rehusar — literally, “refuse” — sounds odd to English ears: it’s the same word, but the ‑f- became an ‑h-. Huh?
This is explained via the pattern of Latin words that began with an f- tended to turn into an h- in Spanish and only in Spanish. See famine/hambre, and huir/fugitive for example.
Refuse and Rehusar follow the same pattern. Both come from the Latin refundere — from which we also get the English, refund. They are all ways of giving back.
This f‑to‑h pattern usually happens with the first letter of the word. But here it is the first letter of the second syllable — because the re- is of course the standard prefix so it didn’t effect the sound pattern change.