A false flag operation is an act committed with the intent of
   disguising the actual source of responsibility and pinning blame on
   another party.
   The term "false flag" originated in the 16th century as a purely
   figurative expression to mean "a deliberate misrepresentation of
   someone's affiliation or motives".^[1][1] It was later used to describe
   a ruse in [2]naval warfare whereby a vessel flew the flag of a neutral
   or enemy country in order to hide its true identity.

References

   1. https://en.m.wikipedia.org/wiki/False_flag#cite_note-1
   2. https://en.m.wikipedia.org/wiki/Naval_warfare