I don't like the expression "boots on the ground.β When did that start? There will be men and women in those boots, and some will die.
@gleick Monsieur le Chat gives this chronology:
πΈπΊ
In short
β’ Origin (as a phrase): ~1950sβ60s (military slang)
β’ Broader recognition: 1990s
β’ Mainstream/common usage: 2000s onward