I'm rereading 'The Healer' by QM. The whole trilogy is great reading. Partway into the story the motto "First In, Last Out!" was referenced, with no one in this far-future story knowing where it originated.
I recalled hearing it before so did a little searching. AFAICT, the US Army Pathfinders seem to be recognized as the originators. This wasn't an in-depth search, so if any of you have more info, please share. Thanks