In airborne school the term used was, "un-assing," i.e., "When you see the green light come on, it's time to un-ass the aircraft."
Deplaning was made popular by the tv show fantasy island, where the little guy would repeatedly say “deplane! Boss, deplane!”
That was a line from a running song at Fort Benning when I was 6, in the mid-60s.
“Airborne, Airborne have you heard?
We’re gonna jump from the big-ass bird!”
I can’t explain why that stuck with me, but it did!
I remember watching platoons double- and quick-timing all over the jump tower field. Soaked in sweat, in a GA Summer.