For the last 25 or 30 years Ive seen many explanations for holes in blades of tulwar, Kris, Dha, kukri  & numerous other blades, shields etc.. 
 
Up until 25 or so years ago, many,many pubs in England were adorned with weaponry from around the world, generally drilled & nailed to the wall, so that they weren't brought into more "current" use on a drunken Friday night.. 
 
I am sure some blades have been drilled for other reasons, but for many thousands there provenance was a 100 years on a pub wall protected from rust by the layers of tar & nicotine. 
 
Many UK dealers and even collectors a couple of decades ago used to plug the hole with copper brass or Gold, then it becomes more of an enhancement & valuable feature. 
 
Spiral
		 
		
		
		
		
		
		
		
	 |