"Pan-pan" actually derives from the French "panne" which roughly translates to "failure" ("en panne" meaning "out of order"). Radio conventions make use of the word "Panne" (pronounced as in a cooking pan), repeated three times, to issue warning of an emergency situation related to some mechanical breakdown. "Panne-Panne-Panne" can then be upgraded to "Mayday" or even "Aaargh" as the situation unfolds.
Useful for clearing the landing runway, but it doesn't help a bit getting the dying propeller back to life.