I have a feeling he's talking less about nauli and more about belly flutters. It's something that's done in belly dance that looks like a very fast movement of the stomach.
^^^^ True enough -- but FBBs rarely do flutters, so I didn't think about it. (The exception was Theresa Hendricks, but she's not to be found here on GWM.)
However ... https://www.youtube.com/watch?v=NctNagkqpHs
Nauli is what you refer to