Cuñado, Spanish for “brother-in-law,” comes from the Latin cognatus, from which we get the near-identical English cognate. How can two words so similar mean something so different?
The Latin root cognatus itself came from the roots com– (meaning “together”) and gnasci (meaning “to be born”); thus, literally, “born together.” So, two words that are cognates are — etymologically-speaking — words that are born together. And brothers-in-law are two men who are not brothers but were, in effect at least, born together as well.
Note also that this is an example of the pattern whereby Latin words with a -gn- generally became an ñ in Spanish. Thus the c-gn-t of cognate maps to the c-ñ-d of cuñado.
Sueño (Spanish for “dream”) and insomnia come from the same root: the Latin somnus, meaning, “sleep.”
The evolution is easy to spot if we remember that the -mn- sound in Latin usually transformed into the ñ in Spanish. See damn and daño, for example. Or autumn and otoño as well.
Thus, the s-mn of insomnia maps to the s-ñ of, sueño.
Apretar (Spanish for “to squeeze”) comes from the Latin pectus, meaning, “chest.” Think of having a heart attack: your chest feels squeezed. It’s not a coincidence that doctors in the USA today still call a heart attack, angina pectoris — that is, “angina of the chest” since pectoral in English today still means “relating to the chest”! The p-t maps to the p-ct, with the -ct- just simplifying into its first -c- sound.
Related: see also Pecho/Pectoral. From the same pectus root, we see other interesting words, following the ch/ct pattern.
The Spanish demasiado (“enough!”) comes from the Latin adverb magis, meaning “more!”.
From that same root magis, we also get the English… master.
It goes to show you: a master is really someone who, as Depeche Mode said, just can’t get enough. So they keep going and going and going, until they’ve become a master.
The m-s root maps clearly to both words.
The Spanish for “to forget”, olvidar, has an interesting cousin in English: obliterate.
Both come from the same Latin root, obliterare, which means, “to cause to disappear; erase; blot out”, but was used in Latin slang to mean “to be forgotten.” You can see this in the o-v-d of olvidar mapping to the o-(b)-l-t of obliterate.
That which is forgotten is, in a sense, obliterated. As the Greeks reminded us: Chronos was a monster who ate his own children. All shall be forgotten!
Obliterare, in turn comes from the Latin root ob– (“against”) and littera (“letter”). Erasing is really just going against the letter itself, after all!