She learned the hand motion in Egypt when she was around 5. You would do this gesture to another person when you want to tease them. Originally, when saying it, you would say “To’ ou moot” (“Explode and die”).
For the sake of my informant’s anonymity, I performed the gesture in the video.
When I first saw the gesture, I thought it was playing on the English saying “Rubbing it in,” but then my informant translated the Arabic that accompanies the gesture. I found it hilarious that the speech and gesture have little to do with one another, but it could fall into the nonsense and taunting categories of children’s folklore (discussed by Jay Mechling in Chapter 5 of Elliot Oring’s Folk Groups and Folklore Genres: An Introduction).*
*Jay Mechling. “Children’s Folklore.” Folk Groups and Folklore Genres: An Introduction, edited by E. Oring, 91-120. Logan: Utah State University Press, 1986.