The lore on historic ethnographic weapons is probably one of the most entertaining aspects of studying them, and quite frankly, most cultural and tribal groups have often had a field day telling these in the queries of curious travellers and tourists.
Myths abound in the west on the intriguing notching of blades as well, and in the years I pursued answers on many of them, there really are none that might be construed as fact, though some have some plausibility.
Some of these are notches on the blades of some 18th c. Austrian cavalry sabres; notches at the back on Meditteranean fighting knives (also a nuance added to original Bowie knives in America) and possibly other instances.
As for the kukri, the 'cho' or choil was profoundly a key feature important to Gurkhas on thier kukri, and while no apparant use has ever been explained satisfactorily for this notch, it was important enough that even military versions produced by the British for the Gurhkas included it. While Spiral and Kronckew are two of the resident authorities here on the kukri now, I recall John Powell who was in my opinion an oustanding authority and author on the kukri, but left here some years ago. It seems that he had rather accepted symbolic purpose for the cho, and most likely toward the goddess Kali I believe it was. The suggestion that it was a bovine hoof was I believe discounted.
I think as Rick has well noted, the kukri is by no means aerodynamically suited as a 'throwing knife', nor would any Gurkha intentionally disarm himself from his key weapon as Knonckew wisely notes. The use of a kukri in this manner in a TV program of course as Ariel says, hardly constitutes worthy evidence, but I am astounded at this incredibly esoteric trivia! You constantly amaze me Ariel!!!
Also, as noted, Gurkhas are quite attached to thier personal kukri, and reluctant to give them over to anyone even for curious inspection.
The well worn and seemingly almost universally used 'chestnut' on a blade needing to taste blood before being resheathed seems used for so many edged weapons its hard to list them all, but I think most derive from the old Japanese myth about Muramasa blades, which were cursed and demanded blood. This propoganda was so effective these blades were outlawed if I recall the tale correctly.
The cho to divert flow of blood away from handle, nonsense, much like these explanations for blade features like the fullers being termed 'blood gutters'. These were actually to lighten and strengthen blade and had nothing to do with flowing of blood, though obviously a dynamic expected in use of the sword as intended.