Tornado
mid 16th century (denoting a violent thunderstorm of the tropical Atlantic Ocean): perhaps an alteration of Spanish tronada ‘thunderstorm’ (from tronar ‘to thunder’) by association with Spanish tornar ‘to turn’.
wiktionary
From earlier English ternado, attested since the 1550s as a nautical term for a windy thunderstorm. [1] From Spanish tronada(“thunderstorm”), from tronar(“to thunder”), from Latin tonō(“to thunder”), from Proto-Indo-European *(s)tenh₂-(“to thunder”). The o and r were reversed in English ( metathesis) under influence of Spanish tornar(“to twist, to turn”), from Latin tornō(“to turn”).
etymonline
tornado (n.)
1550s, ternado, navigator's word for violent windy thunderstorm in the tropical Atlantic, probably a mangled borrowing from Spanish tronada "thunderstorm," from tronar "to thunder," from Latin tonare "to thunder" (see thunder (n.)). Also in 17c. spelled tornatho, tornathe, turnado; modern spelling by 1620s. Metathesis of -o- and -r- in modern spelling influenced by Spanish tornar "to twist, turn," from Latin tornare "to turn." Meaning "extremely violent whirlwind" is first found 1620s; specifically "destructive rotary funnel cloud" (especially in the U.S. Midwest) from 1849. Related: Tornadic.
