Gob-smacking

[JPablo]

What is the meaning and derivation [origin] of the expression "gob-smacking"?

It is probably a British expression, someone near London said,
I thought the event was amazing and gob-smacking. It was breathtaking! It was amazingly special.

Given the context I take that it must be some synonym of "amazing" or "really amazing" but any additional data on it will be greatly appreciated.

[Perikles]

I guess you know gob is a BrE word for mouth (originally a lump of food), and is not used in polite society. Shut your gob = ¡cállate la boca! but probably even less polite.

I'm just guesing that gob-smacking is a reference to when you see something which really amazes you, there is a natural reaction to cover your mouth with your hand (why? to stop yourself swearing?). If something is really surprising, you might do it suddenly and "smack yourself in the gob".

I don't normally use the word

Only a guess.

[JPablo]

Well, that makes sense... I guess it can be to avoid "swearing" or just avoid to utter some kind of exultant and elated cry... that may be 'excessive'.

Thank you, Perikles.

[pjt33]

Originally Posted by Perikles

I'm just guesing that gob-smacking is a reference to when you see something which really amazes you, there is a natural reaction to cover your mouth with your hand (why? to stop yourself swearing?).

Possibly because your jaw dropped* and it's not polite to have a wide open mouth in public.

* "Jaw-dropping" can often be used as a synonym for "gob-smacking".

[JPablo]

Aaaah, good point... (I had to cover my gob/mouth after/before the "Aaaah", but I have not smiley for that)