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 Spanish revancha (“revenge”) comes from the Latin vindicare, meaning — surprisingly — “to vindicate.”
Revenge, after all, is just one way to vindicate yourself!
If we remember the reinforcing re– prefix, we can see that the v-n-ch of revancha maps to the v-n-(d)-c of vindicate.
Parto (Spanish for “birth”) comes from the Latin partus, “brought forth”. That makes sense: a baby is just brought forth into the world.
From the same Latin root, we get the English partum for “birth”. But that word is really only used in one contemporary word today: post-partum depression, the depression a woman gets after childbirth. Yes, post-partum is merely “after-birth”.
The p-r-t root is clearly visible in both words.
Hueso (Spanish for “bone”) comes from the Latin for the same, os. The connection is particularly easy to see when we remember that the H- is perfectly silent in Spanish.
From the same root we get the English ossify — literally, to turn into bone! — but, considering about 4 people know this word, it is easy to remember hueso if we connect it to another word it is related to, albeit more distantly: oyster.
Oyster comes from the Latin for the same, Ostreum, which itself comes from the Latin word os, “bone.” What is an oyster defined by, if not, its hard, bony shell?
The o-s root is clearly visible in all variations!
Gestación (“to develop”) comes from the Latin gestare (“to bear, carry, gestate”) from which we also get — not that surprisingly — the English word gestate. While the original word and the English version focused on developing a baby, in Spanish it has come to be used more broadly: like a business idea develops. The g-st root is clearly visible in both words.