Derretir (Spanish for “to melt”) comes from the Latin terere, “to rub, wear down.” That which is melted is worn down, after all.
Some interesting words we get from the same root in English include:
We can see the r‑t root in all these variations.
Frenar (Spanish for, “to break”, particularly in the sense of, “to stop” — think of, the breaks on your car!) comes from the Latin frenare, meaning, “to restrain,” which itself is from the old Latin frenum for “birdle” — yes, the mouthpiece you put on a horse to, umm, restrain it.
From that same root, we get the English refrain. It is the same frenare root, with the re- added for emphasis. But we have the ‑ain spelling because it comes into English via French, with the refraigner, of course. We can see the f‑r-n maps to the (re)-f-r‑n very clearly as well.
The lesson here is: from restraining someone from doing something (the old sense of the word) to refraining completely from doing it (the new sense of the word) is just a minor step. At least linguistically.
Llenar comes from the Latin plere (“to fill”), as we’ve previously discussed. But here’s another English word that comes from the same Latin root: expletive, yes, that euphemism for vulgar words!
Expletive literally means to “fill” with the expansive ex- prefix which, taken together, mean, “to fill out your words.” An expletive is literally filling conversation with words when you don’t know what else to say!
Volar (Spanish for “to fly”) and its sister vuelo (“flight”) come from the Latin for the same, volare.
From this Latin root, we get the English volley — a volleyball really does fly, doesn’t it? — as well as the English volatile, which is something flying in the sense of being fleeting: it is flying away, time flies.
The v‑l root is so obvious in all, that it’s almost not worth mentioning!
The Spanish for “foam”, espuma, comes from the Latin for the same: spuma. And this Latin comes from the Proto-Indo-European root *(s)poi-moi from which we also get the English… foam.
How so? Because the PIE root p- very consistently became an f- as it evolved into German then English, but this transformation never happened when it became Latin and then Spanish. Note words like foot/pie and father/padre.
Thus the f‑m of foam maps to the (s)-p‑m of espuma very clearly!