Gobsmacked!

Recently I have been noticing the word "gobsmacked" being used. I was never sure what it meant, so I decided I would do a little bit of research on it. Here is one of the definition from the place I found called the internet:

gob·smacked

/ˈgɒbˌsmækt/ Show Spelled [gob-smakt]    

adjective Chiefly British Informal.

utterly astounded; astonished.

 

I had thought that it had to do with being surprised by an outcome, as that seemed to be the context where it was used. I did not know that it's origin was from England, specifically Northern England. One of my nieces interned in Northern England, so she may have heard this expression while she was there.

 

Lately where I have seen it used has been in "trendy" circles. This seems strange since it is considered "informal" and "slang". I wonder if those using it really know of it's origin? I doubt if I ever use it since I am not very "trendy", although it might be fun if others don't know what I am talking about! I am gobsmacked!