Bombast
Etymology
From Old French "bombace" (cotton wadding), from Late Latin "bombax" (cotton), an alteration of "bombyx" (silk). "Bombast" first meant the cotton stuffing used to pad out clothing, then shifted by metaphor to language stuffed and puffed up to seem larger than its content.
noun · /BOM-bast/
Inflated, pretentious language with little real substance behind it.
What it names
Speech that is all padding — grand-sounding and empty — a common disguise for weak arguments.
Example
Strip the bombast from the speech and you were left with a single vague promise.
Related idea
Bombast is inflated language empty of substance; being grandiloquent is speaking in a lofty, high-flown style, which may still say something true — bombast is grandiloquence with nothing inside.