The Spanish word 'necio' (meaning 'foolish' or 'ignorant') comes from the Latin word 'nescius', which also meant 'ignorant'. The Latin word itself is a combination of two parts: the negative prefix 'ne-' and the verb 'scire' meaning 'to know or discern'. So literally, 'nescius' meant 'not knowing' or 'without knowledge', which evolved into the modern Spanish word for someone who is foolish or ignorant.

A related Spanish word is 'necedad' (foolishness or stupidity), which is derived from 'necio'. While these aren't necessarily simpler, they form part of the same word family in Spanish.

The Latin root 'scire' (to know) that appears in 'necio' has given English several related words, though they're opposites in meaning since they don't have the negative prefix. These include 'science' (systematic knowledge), 'conscious' (aware, knowing), and 'prescient' (knowing something before it happens). The word 'nice' also surprisingly comes from the same Latin 'nescius', though it took a very different path: it originally meant 'foolish' or 'silly' in Middle English before gradually developing its modern positive meaning.