tornado: [16] Tornado appears to denote etymologically something that ‘turns’, but this is due to a piece of English folk-etymologizing. Its actual source is Spanish tronada ‘thunderstorm’, a derivative of the verb tronar ‘thunder’ (which in turn went back to Latin tonāre ‘thunder’, source of English astonish, detonate, etc). It was at first used in English for a ‘violent thunderstorm’, but confusion with Spanish tornado ‘turned’ had converted tronada into tornado, and as early as the 1620s we find it being applied to a ‘whirlwind’. => thunder
