I’ve seen this gesture in movies and my friends use it sometimes. You use it when you say goodbye to someone and you kinda tap on the side of your forehead with two fingers. I’ve attached an image with Brad Pitt doing this in once upon a time in Hollywood. Does anyone know what this gesture is called? Where it comes from, and what it means? Thanks!
I’ve never actually heard a name for it. Broadly speaking, I would just call this a kind of salute, and, specifically, a two-finger salute. Wikipedia has an entry for this:
The two-finger salute is a salute given using only the middle and index fingers, while bending the other fingers at the second knuckle, and with the palm facing the signer.
It looks like he is performing a humorous salute.
It is difficult to say from a motionless picture, but judging by the proximity of the middle and index fingers I would suggest he is giving a tongue-in-cheek salute, like these other actors:
Usually, a salute is a sign of respect and/or acknowledgement of orders from a superior, but in casual settings it is sometimes used humorously as a farewell gesture. It is very common in the military.
As for its origins, this Wikipedia page states the following:
According to some modern military manuals, the modern Western salute originated in France when knights greeted each other to show friendly intentions by raising their visors to show their faces, using a salute. Others also note that the raising of one's visor was a way to identify oneself saying "This is who I am, and I am not afraid." Medieval visors were, to this end, equipped with a protruding spike that allowed the visor to be raised using a saluting motion.