Past tense of 'flack': to work as a press agent or public relations person, or to promote aggressively.
From 'flack' (1940s slang), possibly from the name of Eugene 'Gene' Flack, an early press agent, or from Yiddish 'flak' meaning chatter or criticism.
The term 'flacked' became Hollywood slang right when the PR industry invented itself in the 1940s, and it's still used today when someone's trying to sell you something through aggressive media manipulation.
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