The Spanish caja (“box”) comes from the Latin capsa for the same.
This gives us a surprising connection to some English words that, on the surface, sound very different than caja:
The Latin turned into the Spanish through an interesting pattern: the -sh- sound in Latin consistently turned into the -j- sound in Spanish (at first retaining the original pronunciation, but then under the influence of Arabic, grew to the throat-clearing sound). With caja, we have a slight variation of the pattern, where the -ps- sound turned into the -j- sound. Thus, the c-ps maps exactly to c-j.
The “sh” sound — often represented in writing as an “x” — transformed in all different ways to the “j” letter (and the accompanying mouth-clearing sound, influenced by Arabic) as late Latin turned into Spanish. See lots of examples: sherry/jerez, for example.
Here’s another: the common Spanish word, dejar, meaning, “to leave to the side” or “to put down” or to “put away” or to just “let go.”
Dejare comes from the Latin laxare, meaning, “to loosen”. From this same root, we get a few English words — which did not go through the x-to-j transformation Spanish did including:
Quejar, Spanish for “to complain” doesn’t seem related to any English equivalent.
But upon closer look, it is a first cousin of both quash and squash.
All come from the Latin quassare, meaning, “to shatter.”
The relationship is easy to see if we remember that the Spanish -j- sound used to be the Latin -s- sound (and many variants, like -ss-, -si-, -sy-, -sh-, -ch-, etc).
Thus, the qu-j for quejar maps to the qu-sh of quash and the sq-sh of squash.
Complaining, it seems, is a form of quashing (squashing?) your opponent!
Enojar, Spanish for “to get angry”, has a fun cousin in the English, annoy.
Both of these (along with the French for “worldly boredom”, ennui) come from the Latin inodiare, meaning, “to hate”. The Latin in- adds emphasis to the odium, Latin for “hate”.
We can see the parallels in all with the open vowel, followed by the -n-, followed by a -y- sound, although in Spanish the -y- sounds (and its corresponding -x- and -sh- variations) often turned into the -j- sounds, as it did here. Thus, the a-n-y maps to the e-n-j.
Hatred, then, dissipates and weakens over time. In English, hatred weakens into mere annoyance. In Spanish, hatred weakens into just anger, enojo. And, best of all, hatred in French weakens into a world-weary boredom of ennui.
One of our favorite patterns of sound change between English and Spanish is the sh/j shift: under the influence of arabic, many words that had a “s” or “sh” or “sy” or “ch” sound in Latin, started to be pronounced with the throat-clearing sound and written with a “j”. See sherry/jerez and chess/ajedrez or syrup/jarabe, for example.
Another example of this pattern is the Spanish word for “juice”, jugo. It comes from the Latin succus meaning, “juice” (particularly sap, or juice from plants).
From this Latin root succus we also get the English… suck.
Yes, if it sucks — it is juicy! Literally!
We can see the mapping in the s-c to j-g mapping. The “c” and “g” sounds are similar and often interchanged.
Interestingly, in Spain they do not say jugo to mean “juice”; instead, they say… suco. Suco, funnily enough, also comes from the same root of succus. It is just the variation that never underwent the arabic “j” transformation.
From the same root we also get the English succulent, although we do not get the superficially similar English juice, which comes from the Latin ius, meaning, “sauce.”