Is it ensure, insure, or assure?
"courageous," 1811, originally of fist fights. To stand (someone) up "fail to keep an appointment" is attested from 1902. Stand-up comic first attested 1966.
To persist and endure against rigors; take it: I've had at least seven lifetimes on Seventh Avenue, mainly because I've learned to stand the gaff
[1896+; fr gaff, the steel spur attached to the leg of a fighting cock]