drop a bombshell, to

drop a bombshell

To reveal something that is very surprising or unexpected. Whoa, you can't just drop a bombshell like that and leave—I need details about your new boyfriend! When we got a tip that the newspaper was about to drop a bombshell about our candidate, we all wondered what information they could possibly have.
See also: bombshell, drop
Farlex Dictionary of Idioms.

drop a bombshell

Make an unexpected or shattering announcement. For example, Bill dropped a bombshell when he said he was quitting. This expression, which alludes to the destruction caused by a falling bomb, dates from World War I.
See also: bombshell, drop
The American Heritage® Dictionary of Idioms by Christine Ammer.

drop a bombshell

COMMON If someone drops a bombshell, they suddenly announce a piece of bad news. Next day the bombshell was dropped on the front pages of the newspapers: the company had gone into voluntary liquidation. My ex-wife is on the phone and she drops a bombshell. Sue, our daughter, is leaving the country.
See also: bombshell, drop
Collins COBUILD Idioms Dictionary, 3rd ed.

drop a ˈbombshell

announce something which is unexpected and usually unpleasant: It was then that he dropped the bombshell — he wasn’t planning to come with us.
See also: bombshell, drop
Farlex Partner Idioms Dictionary

drop a bombshell

verb
See drop a brick
See also: bombshell, drop
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions

drop a bombshell, to

To announce sensational news. This metaphor dates from World War I and likens the devastation caused by falling bombs to the shock of suddenly receiving unexpected tidings. “The letters do not drop any historical bombshells,” wrote a Manchester Guardian reviewer in 1928. See also bolt from the blue.
See also: drop
The Dictionary of Clichés by Christine Ammer
See also:
  • drop a bombshell
  • explode a bombshell
  • explode
  • drop a bomb
  • have a kick to it
  • have a kick to it/them
  • double buffalo
  • take it easy
  • take it/things easy
  • shut the door on (something)