The place from which a fart, or a toot in this case is shot out of aka the bum hole.
When I was younger my uncle touched my toot shoot
This expression would be used by someone who has a degree of uncertainty about whether they have an urge to fart or whether he or she might actually shart or fully shit themselves.
I'm either about to toot or shoot right now, shall I risk it anyway?
I just finished my second bowl of nachos and I can't tell if I'm about to toot or shoot.