Flabbergast Definition

Origin of Flabbergast

• Origin uncertain. Hotten says it is from Old English; Whitney and Smith suggests flabby or flap (strike) + gast (astonish); The Imperial Dictionary connects it with flabber (related to flap, to strike) + the root of aghast, and notes that flabagast may have been the root (to strike aghast); first documented as slang in 1772; Cassell gives it as dialectical from Suffolk, from flap or flabby + aghast, possibly related to Scottish flabrigast (to boast) or flabrigastit (worn out with exertion); Smith relates it to flab (to quake) or flap (to make a flap over something) + Middle English agasten (to terrify), and relates it to aghast, ghastly and ghost

  From Wiktionary

• Origin unknown

  From American Heritage Dictionary of the English Language, 5th Edition