Gitmo -- not in OED -- HDAS has 1959 -- (Navy) slang for Guantanamo Bay "Home on Leave" Indiana, PA _Indiana Evening Gazette_ 1949-08-26, p. 8 col 3. "Before coming home, Midshipman Balint went on a summer cruise for seven and one-half weeks with a week's stopover in England and several weeks in Gitmo, Cuba."