I don't like the expression "boots on the ground.” When did that start? There will be men and women in those boots, and some will die.

@gleick Monsieur le Chat gives this chronology:
🍸😺

In short
β€’ Origin (as a phrase): ~1950s–60s (military slang)
β€’ Broader recognition: 1990s
β€’ Mainstream/common usage: 2000s onward