Is it ensure, insure, or assure?
1938, from German Flak, condensed from Fliegerabwehrkanone, literally "pilot warding-off cannon." Sense of "anti-aircraft fire" is 1940; metaphoric sense of "criticism" is c.1963 in American English.
: The flack description is also worth quotingnoun
: his publishers, who flack it into a best seller/ He's not flakking for ulterior motives
[origin unknown; said to be fr the name of Gene Flack, a moving-picture publicity agent, and first used in the show-business paper Variety; probably influenced by flak]
[fr German Fliegerabwehrkanonen, ''antiaircraft gun'']