It's a mix of everything. There are a lot of pre-european naming, but then you have not only spanish influence but also italian (in the south) and even african. A good example might be aguacate for avocado, which is old Nahuatl, but it's palta in Argentina. Chocolate is another famous one that's from Nahuatl i think. Meanwhile 'green beans' have literally 4 completely different names, no joke.