FliegerAbwehrKanone Literally means "Flier Defense Cannon " Designation used for AA weapons (FLAK guns) During World War I, this term was used by Allied airmen to describe the shell bursts from such weapons, which has become the current accepted meaning of the term
If you get a lot of flak from someone, they criticize you severely. If you take the flak, you get the blame for something. The President is getting a lot of flak for that