The tongue idea may be speculation, but it is interesting. It is certainly not uncommon to see Chinese and other steel weapons with the blade coming out of the open mouthed head forming the guard.
I wonder about the shape based on the long triangle of the original stone "handaxe" that served as models for later celts. Louis Leaky speculated that some handaxes might have been designed for throwing. If so, they would have been held from the tip to put the greater mass of the wide end on the end of a lever arm. The kawas of Vanuatu was a sort of stone throwing stick, but the oldest versions were basically stone hand axes in one piece with a stone handle. I wonder if the patu didn't start as something of the sort. They seem too high value to throw around, but I could imagine that one would have stopping power as a close quarter missile. Slings and spears propelled by cords were excellent Maori distance projectiles, so perhaps in later use they became solely high status clubs.
Well, it is fun to speculate...
