I've just heard the announcer on the BBC before Eastenders say..

"Drops a bombshell"

I can think of a few other sayings I have no idea where they originate if anyone can shed any light I'd be interested to know.

The first one I just mentioned..

"Shed any light" Why shed? why not shine?

"Dutch courage" and "Going Dutch"

"He got off scot free" Is Scot a person or referring to Scottish people?

"Fit as a fiddle" Can a fiddle be fit?

"Ship shape and Bristol fashion"

And one I hear on movies and American TV shows

"Take a raincheck" Not used so much here I don't think

Any others anyone can think of?