Thunderclap or "SMACKING THE EARS"The following excerpt is from Col. Fairbairn's book "Get Tough"...NO. 23 - SMACKING THE EARS
This method should be applied when your opponent has no protection over his ears.
Cup your hands, keeping the fingers and thumbs bent and close together, as in Fig. 76.
Strike your opponent simultaneously over both ears, using five to ten pounds force (Fig. 77).
Note. - This will probably burst one or both ear-drums, give him at least a mild form of concussion, and make him what is known in boxing circles as "punch-drunk." You will then have no difficulty in dealing with him in any way you wish.
So that you may realize what the effect of a blow given as above is like, apply it on yourself, as in Fig. 77A. Care must be taken to use only half a pound force with each hand.From Cold Steel by John Styers…The Palm.
The results of a punch to your opponent's head in the usual manner are, in many instances, not felt until the next day, but a full resounding slap on the face or base of the skull will rock your opponent right then and there. A good single or double slap across one or both of his ears will drop him on the spot.
If enemy has you in front grip and both your hands are free, slam palms over his ears. Result is like a blast concussionFrom the old Okinawa manuscript Bubishi, the 48 original techniques of Karate via the Okinawa Karate
Seems like it worked quite well for this gent...
Concussion blow to the ears from Combat Jiu Jitsu by S. R. Linck
This text is from 1943 so apparently this type of slap or blow isn't anything new.