To the best of my knowledge, the origin of the phrase was in the Army. A spade is officially known as a “personal entrenching tool”, and many other common things also have overly complex names. That’s why they love acronyms so much. As a veteran and a former POW, I would be more inclined to think Mr. Vonnegut picked it up from that context.
But this gets me to thinking: how many other phrases come from similar innocuous roots, but due to words evolving we assume more nasty origins?
“A snowball’s chance in hell” evolved from the phrase “[19th century epithet for a Chinese person]'s chance in hell” which was at best a reference to the fact that there were few Chinese Christians, but more often than not was just plain old racism.
Yeah, the Blaxpolitation-styled Bond movie where this is used is pretty cringeworthy. i don’t think the phrase is racial in origin though - it’s used in the Importance of Being Earnest in the original sense, with humour derived from class snobbery around proximity to manual labour.
“When I see a spade I call it a spade.”
“I am glad to say that I have never seen a spade. It is obvious that our social spheres have been widely different.”
Speaking of over-complexity, when I worked for the local council, fire drill was known as ‘two-stage progressive horizontal evacuation procedure’. God knows what they came up with for buildings that had stairs in them.