Suspect and the Spanish equivalent, sospechoso, are easy to identify and obviously the same word, both from the same Latin root, suspectus.
That’s not the interesting part. Rather, as Latin evolved into Spanish, the Latin sound ‑ct- turned into the Spanish ‑ch- sound. Think lactose/leche or octagon/ocho.
And suspect falls exactly into this pattern: the English s‑s-p-ct maps exactly to the Spanish s‑s-p-ch.
Luchar, Spanish for “to fight”, doesn’t sound like its cousin reluctant — although of course everyone is reluctant to fight. But the relationship is closer than it seems.
Reluctant comes from the Latin roots re- (“against”) and luctari (“to fight”). Reluctance is to fight against what should be done — literally.
From luctari, we also get the Spanish for exactly the same, “to fight.”
But they don’t sound similar. How did luchar evolve?
Interestingly, in most Latin words that had a ‑ct- sound, this ‑ct- sound evolved into ‑ch- as Latin evolved into Spanish. Think about night/noche and eight/octagon. The same pattern explains luctari turning into luchar.
We see this relationship clearly with the l‑ct to l‑ch mapping between the two.
The Spanish mancha (“spot” or “stain”) comes from the Latin for the same, macula.
From the Latin macula, we get the English… immaculate — which literally means (knowing the negation prefix of im-) “without a stain.” So the immaculate conception truly was perfect!
How this sound changed was interesting: often Latin words with a ct- or cl- or other hard letters after a c- sound turn into a suave ch in Spanish. For a distant example, see duct and ducha, or nocturnal and noche. (The ct- is much more common than the cl‑, but they’re cousins!) Thus, we can see the m‑ch of mancha mapping to the (im-)m‑cl of immaculate.
The law and the good, in European languages, are associated with straight lines; the bad with the crooked. Think about the word crooked itself, literally! Or about right/rectangle, or the Greek ortho- for straight, hence, orthodox as well as orthodontics.
This is why it makes sense that Derecho — Spanish for straight and also for law — comes from the same Latin root that gives us direct.
The “ct” in the original direct turned into a “ch” in Spanish, in the usual pattern of “ct” turning into “ch” as Latin grew into Spanish.
The Latin for “eight” is Octo, from which we get the English Octagon.
Since most Latin words with a ‑ct- sound, like Octo, had the ‑ct- turn into a ‑ch- as the language evolved into Spanish, it is no surprise that eight in Spanish is ocho.
This same pattern manifests itself in noche/nocturnal, leche/lactose, and is one of our favorite patterns here at ForNerds!