Where did the term "pink slip" come from?

Question...

My boss was not happy with my performance and went ahead and canned me. Apparently he didn't appreciate me rolling in late each day, but hey, sleep is important to me. The official notification he handed me was on a piece of ivory paper, and this got me wondering, where did the term "getting the pink slip" come from?

-- Sleepyhead in Solana Beach

You sound like a man with his priorities in order. So I wish I could be more specific with my answer. The phrase-origin brain trust is its usual evasive self on this one. The term is definitely American, dates from the Nineteen Tens, and comes from the practice of putting a pink "you're fired" slip in the offender's final pay packet. Who started it? Nobody knows. Why pink? Why was the practice widespread enough to spawn a popular expression? Ditto.

"Fired" is easier. Again American, 1890s, a short form of the already-popular term "fired out," as in ejected with force from someplace you're not wanted..."They fired me out of the bar last night." Gun metaphors are at the source, of course. "Canned" is a bigger mystery. Meaning "fired," it long predates "can" as a toilet or a jail or your butt. You could have been canned in America as far back as the 1880s. That's about ten years after people began buying food in mass-produced tin cans, so maybe that's the connection. They stick you in a can and ship you out of the company. My personal wild speculation is no worse than what etymology eggheads get paid the big bucks for. Just because you get it free in the Reader is no reason to sneer. Americans love slang and wordplay. And I guess Sleepy is going to have plenty of time for that now. And luckily the Reader will fit his new budget just fine.