The Latin words beginning with the harsh gu- sound generally have the same root and are parallel with the English w- words. Think, William and Guillermo, for example. The gu- and w- sounds do sound alike, if you say both in a thick way.
Guerra and War are another great example of this pattern. The English war comes from the French guerre, which in turn comes from the old German verwirren — meaning “to confuse people.” War is confusing indeed and confusing people is indeed a form of warfare.
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.
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!
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).
Thus, the w-l-s of Wales maps exactly to the g-l-s of Gales.