To bombast or speak in a loud, grandiose, inflated manner; to bluster or rant.
From 'bombast,' which itself comes from 'bombax' (cotton), originally referring to padding and later metaphorically to inflated speech.
Bombast originally meant 'stuffed with cotton padding,' and then people applied it to speech that was similarly 'padded' with meaningless words—pure English metaphor at work.
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