First recorded around 1765–75.
A variant of flabagast, which may be a combination of flabb(y), \"hanging loosely or limply\" or flap, \"a blow given with something broad and flat,\" and aghast, \"struck with overwhelming shock.\"
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\r\nEXAMPLES OF FLABBERGAST\r\n

The magician's disappearing act never failed to flabbergast the audience.
The unexpected news about the new mayor flabbergasted the community.

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ED50

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