The assassin choke in BJJ is a choke submission initiated from the crucifix position where the aggressor chokes their opponent using their own gi’s lapel or belt.
Baret Yoshida: https://www.instagram.com/baret75/reel/DBsVVthxiIN/ https://www.instagram.com/baret75/reel/CwCLnbAsdOt/ https://www.youtube.com/watch?v=IW7I7uHvDmU https://www.youtube.com/watch?v=5iovrPoQhgc
In this video, Baret Yoshida talks about how there was some controversy after he choked someone with the assassin choke using his belt. He mentions how he ties his belt in a manner conductive to using it for these types of chokes and several details regarding controlling an opponent with the crucifix prior to attempting the assassin choke.
https://www.youtube.com/watch?v=9UFuhp40ylY