off the record
Unofficially, in confidence, not for publication, as in What he was about to say, he told the reporters, was strictly off the record. Probably alluding to striking evidence from a court record (because it is irrelevant or improper), this term came into wide use in the mid-1900s, especially with reference to persons who did not wish to be quoted by journalists. For antonyms, see go on record; just for the record.
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