Where does “fuente” come from?

fuente (Old Spanish) comes from Latin fons, from Latin fontis — genitive singular of fōns.

Ancestry of “fuente”, step by step

Step	Language	Word	Meaning
1	Latin	fons	a spring, a fountain; fresh water, spring water;...
2	Latin	fontis	genitive singular of fōns

fuente — Etymology, Origin & Word History | Etymology Explorer