The common Spanish word dar (“to give”) comes from the Latin for the same, dare.
From the Latin root, we get the English… mandate (“to give with your hand” — thus related to mano as well): what is a mandate if not a written order to give to someone? The best mandates are when you deliver them yourself anyway, not through intermediaries. The dare connection explains where the ‑d- after the hand comes from!
Another English word from the same root: tradition. That word comes from the Latin tradere, literally, “to hand over” — the tra- is the same trans- root (“over”), while the dere is the same “give.” In today’s way of walking, we’d say that tradition is what is handed down to us: it is what is given to us. Literally. ANd you can see the ‑d- in the word from dare as well clearly!
Fervor is really just an intense passion heating up. Thus we shouldn’t be surprised that it comes from the Latin root fervere (“to boil”), from which we get the Spanish for the same (“to boil”), hervir.
The seemingly unrelated words are connected through the common transformation of Latin words beginning with an f- into an h- in Spanish, such as fig and higo, and fable and hablar.
Thus, the f‑r-v of fervor maps to the h‑r-v of hervir.
The Spanish tener (to hold) comes from the Latin tenere for the same.
From the same root tenere, we get the English tenet — think about it, you hold your beliefs.
And it gets even better: from tenere, we also get the English suffix ‑tain, as in maintain, sustain, contain, detain, obtain, and entertain. And the -tain words map almost identically to the Spanish suffix of the same, the same -tener!
For example, mano, the Spanish for hand, is the same mano in maintain (or mantener, in Spanish) — which thus literally means, “to hold in your hand”!
The Spanish correr, “to run” seems completely unrelated to the English horse. Looks can be deceiving.
Correr comes from the Latin for the same, currere. Currere, in turn, comes from the Proto-Indo-European root *kurs, which also means, “to run” — just like horse does! Both have the same common ancestor.
The weird thing is: how did the PIE *kurs turn into horse, they sound so different.
The explanation is that, in the Germanic languages like English, the k- sound turned into the h- sound. But in Spanish, the original k- sound remained, although usually written with a c-.
This explains many parallel words that have c- and h- sounds that map to each other between Spanish and English, like heart/corazon and head/cabeza.
The Spanish for “horn”, cuerno (and its variations, like the ever-present cornudo), and the English horn are both originally the same word in the ancient languages.
One of the most interesting sound shifts is the Indo-European “k-” sound remained the same into Latin and then Spanish (the Latin cornu for the same) but became an almost-silent “h-” in the Germanic languages.
Thus the c‑r-n in Spanish parallels exactly the h‑r-n in English.
There are lots of awesome and subtle examples of this pattern, such as Corazon/Heart.