Flabbergast /fla-bər-ˌgast/ verb

Definition:  Flabbergast means to overwhelm with shock, surprise, or wonder, to overcome with bewilderment, and to astound.

Etymology: The precise origin of flabbergast is unknown. It first appeared in print in England in 1772 in the Annual Register of World Events, where the author, known only as “Observator,” bemoaned the use of “new words” with no social respectability. 

Flabbergast was apparently so new that it did not appear again for thirty years, and then not until 1823 when a dictionary entitled Suffolk Words and Phrases listed it. It was cited specifically as flabbergasted, meaning astonished or confused. Flabbergast may have come about as an arbitrary invention derived from flabby, flap, and aghast, or possibly as a variant of flabagast.

In a Sentence

It flabbergasts me to see the loss you and your family have suffered.

Your decision to abandon your wife, your children, your job, and your country flabbergasts me.

You flabbergast us today, tomorrow, and forever.

No one can surprise or flabbergast her, always perfectly calm, reflective, even in temperament and composed.

Synonyms 

Astonish, Astound, Shock

Antonyms 

Pacify, Assuage, Soothe