I saw this throw demonstrated earlier today in a children's judo class. The tori starts in a headlock (or perhaps puts their own head into one), pushes their inside arm through to grab at the back of the uke, and then steps through to catch their ankle. As the uke goes over backwards, the tori does a breakfall over the top of the uke (or to the side of their head if they're trying to be gentle).
The teacher didn't know the name of this throw, and said that it wasn't in the Kodokan set. He was unsure if there is a formal name for it.
Does this have a name? Most of the headlock throws I've found on Youtube look very different and have the person performing the headlock completing the throw. It seems like it should be sutemi waza, but the lists of sutemi I can find don't have anything that sounds/looks like it.
Tori (red) is in headlock (or allows himself to be put in one) by uke (blue). Tori is facing away from camera, uke facing camera. Tori's right leg will step between uke's legs.
Tori's right arm is still in front of uke, but tori shoots (squirms?) his right arm through to grab uke behind his back (or in the judo-illegal version, grabbing at the uke's right leg).
Tori's right foot shoots through and catches uke's right foot. At the same time, tori pushes forward so uke falls backwards, balance having been broken. Uke lands on back, and tori breakfall/rolls either to the side of his head (or in the mean version), right over the uke.