Gastar (Spanish for “to spend”) has an interesting first cousin: waste.
Both come from Latin vastare (“to lay to waste”) which in turn comes from vastus (“empty.”)
The v- sound of vastare turned into a gu- sound as Latin turned into Spanish. But in English, this French word took on the more Germanic w- sound. Thus, although not directly descended from German, it does follow the common g-/w- pattern (guerra/war).
We can thus see the g-st map to the w-st clearly.
After all: spending money is wasting money!
Thus, the w-l-s of Wales maps exactly to the g-l-s of Gales.
The “W” sound is a classic Germanic and Anglo-saxon sound. Harsh, it is.
Interestingly, the Germanic and English words with the w- become the gu- sound as these words evolved into Spanish. Yes, in this case, the Germanic and English words — centuries ago — made its way back into Spanish rather than the more common pattern of vice-versa!
One example: the name William maps to the Spanish name… Guillermo. I first discovered this because I was once in a bookstore in Buenos Aires and there was a book “Enrique IV” by “Guillermo Shakespeare”. I needed about a minute to figure out what was happening (Enrique is Spanish for Henry).
The Spanish Guardar, meaning “to watch over or care for”, and the similar Guardia (the ER! Emergency Room) are both cousins of the English ward and warden. Huh?
Both come from the same Proto-Indo-European root, *wardo, also meaning “to take care of”.
But, as Latin turned into Spanish, the initial W- sound turned into a G- sound but remained the same in English.
Therefore, the Latin-ish G-R-D maps to the Germanic W-R-D. Ahhhh!
However, what is noteworthy is that the -w- becomes a -g-. At first, that seems odd. But then, we remember the -w- to -g- transformation: that in a lot of Germanic words, when they’re brought into Spanish, the -w- sound becomes a -g- sound. Think war/guerra, for a great example.