Nice means pleasing, agreeable, delightful and much more. It has so many meanings that the word can be applied to almost everything we consider “nice”. It comes from the Latin nescius, silly, foolish, ignorant. Its meaning has been changing from timid to fussy, and from fussy and fastidious to delicate, and then agreeable and kind. People use words, and give them new meanings, out of ignorance, or perhaps as an attempt to be playful and fashionable, and “different”.
The Spanish necio did not evolve or change, and has retained the original meaning of ignorant, silly, foolish. (DRAE: “Necio. Ignorante y que no sabe lo que podía y debía saber.”) Both necio and nice come from the same root but now have different meanings.