I think it's original. 
Not because I can say a reason to do it, but because I've seen it before on Spainish swords and daggers, and because it resembles the way the upcurved rear quillon of a kris and some other swords (kampilan for instance) molds against the swell of the hand between thumb and palm.
		 
		
		
		
		
		
		
		
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