It’s an expression of sympathy for the most junior person; tongue in cheek. That’s mainly it. And of course, it also carries some generic unionist meaning about “Taking care of our own”. But never was it associated with furloughs until someone decided that’s what it meant. If the interpretation was about furloughs, nobody ever told the group at large.
If someone has more specific history, feel
free to share. Anyway, most of us want to help save furloughs and hopefully we can, somehow. But it’s not a specific duty or creed of the United pilot to do so, culturally speaking.