FLOTUS, meaning the First Lady of the United States, was
probably first used publicly in 1983 by Donnie Radcliffe of the
Washington Post who wrote that the secret service use POTUS and
FLOTUS to refer to the President and the first lady. POTUS was
first used to designate a telephone line in the West Wing's Cabinet
room, between President Nixon and his Cheif of Staff H.R. Haldeman
in 1969. Then POTUS disappeared for a while and was made popular
again in a 1977 White House Novel, "Full Disclosure," as a pet name
adopted by the unmarried president's paramour photographer. She
felt calling him Mr. President was too formal given their intimate
relationship, but calling him by his first name didn't seem exactly
appropriate either, so she settled on POTUS.