An undesirable individual; a person out of favor. The term persona grata is Latin for “an acceptable person” and was used to describe diplomats acceptable to the government to which they were accredited. When such a person was, for some reason, no longer acceptable, he or she became persona non grata and would have to be recalled. From the late nineteenth century on, however, the term was also used more loosely for someone who had gotten in trouble or simply was disliked. The OED cites a 1958 issue of the Oxford Mail: “The BMC management should have known that the introduction of two or three people who are persona non grata with the other 350 men in the shop would create difficulty.”