As with mayday (from venez m'aider, "come help me"), the urgency signal pan-pan derives from French. In French, a panne ([pan] — /pɑːn/, "pahn") is a breakdown, such as a mechanical failure. In English, it is also sometimes[vague] pronounced as /pæn/ ("pan"). A three-letter backronym, "possible assistance needed" or "pay attention now" derives from pan. Maritime and aeronautical radio communications courses use those as mnemonics to convey the important difference between mayday and pan-pan.
Pan Pan Pan is also the term used in the skies over Florida and S Alabama for simulated emergencies in Navy flight school. While the call used in ordered emergencies are supposed to just be over the intercom system (ICS), a harder pull on the switch would send them over the air. To avoid ATC and others from responding should the student ‘exceed his detent’, Pan pan pan told everyone it was simulated. In 16 years, never heard it for real. Mayday on the other hand is action stations.