"Tarab hand" is what I call this position of the hand to the side of the face in the Soheir videos. It's not something other people call it - just to note- it's my term. ? Take a look at this CD cover photo of singer Ahmed Adaweya for an idea of what I mean. While he is associated with Shaabi music (as opposed to high art music), he was known for his artistic, deep-feeling interpretation of maqam, which is part of achieving and producing the state of musical ecstasy known as tarab.

I learned about this gesture that is associated with tarab (because of the singers tuning their notes off of their own facial resonance, presumably) from UCLA ethnomusicology professor Ali Jihad Racy, whom I studied with at the Arabic Music Retreat. We had a conversation about this at the time, that the gesture might have been simply borrowed from dancers tapping into this recognizable image - just my speculation but it seems plausible. This is what I see Soheir doing, but that is my interpretation. I need to ask a few Egyptian dancers to see what they say about it.

Grab Jihad Racy's great book on tarab for more on the subject of tarab and improvisational music in the Arab world. It's an academic book but a very accessible read, in my view.