The Spanish hechizo (“spell”; nothing to do with the letters in words, but what a witch casts on you!) comes from the Latin facticius (“made by art”; “artificial” — indeed, that which is artificial is just something not occurring naturally but instead made by art!).
But how did artificial change to mean “spell”? Think about it this way: casting a spell goes against nature — it’s what the wicked, crazy and profoundly unnatural woman does! Think of the three weird sisters in Macbeth, and how they unnaturally stir up all the elements!
From hechizo (more specifically, from it’s Portuguese twin cognate, feitiço), we get the English fetish. How? Well, you have a fetish when the recipient casts a spell on you to become obsessed with the object of your fetish, right? Enough said!
That root facticius turned into hechizo by changing via two common patterns: the initial F in Latin tended to turn into an H as Latin turned into Spanish (compare fig and higo, or fume and humo!) and the ‑ct- tended to change to a ‑ch- (compare noche and noctural; or ocho and octagon). Thus the h‑ch of hechizo maps to the f‑sh of fetish.
The Spanish hongo, for “mushroom,” doesn’t sound anything like its English counterpart “mushroom.” But it does come from the Latin fungus from which we get the English synonym for mushroom… fungus.
The relation between hongo and fungus is easy to remember if we remember that, as Latin evolved into Spanish, the initial f- (followed by a vowel) usually transformed into an h-. Thus, the f‑n-g for fungus maps exactly to the h‑n-g of hongo.
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.
The Spanish “hablar” (“to talk”) comes from the vulgar Latin “fabulari”, also meaning, “to talk” — hence the English, “fable”.
This gets very interesting very quickly, so note:
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!