'Tornado' was probably 'tronada' (thunderstorm) — misspelling changed its meaning from thunder to twisting wind.
A violently rotating column of air extending from a thunderstorm to the ground, often visible as a funnel cloud.
Probably an alteration of Spanish 'tronada' (thunderstorm), from 'tronar' (to thunder), from Latin 'tonare' (to thunder), from PIE *ton- or *(s)tenh₂- (to thunder, to resound). The word was reshaped by folk etymology to resemble Spanish 'tornar' (to turn, to return), from Latin 'tornare' (to turn on a lathe). The earliest English uses (1550s) referred to violent thunderstorms at sea off the West African coast, not rotating wind columns — the modern meteorological meaning developed later. Key
'Tornado' is a word that changed its own meaning through a spelling error. It started as Spanish 'tronada' (thunderstorm, from 'tronar,' to thunder), but English speakers reshaped it to look like it came from 'tornar' (to turn). The misspelling stuck, and the word's meaning shifted from 'thunderstorm' to 'turning wind' — the false etymology became the true definition.