During a recent trip in Sarawak, I was fortunate enough to have the chance to buy a local parang. The main blade is called Bukok while the sheath is called Sibong. Here is mine
The design is ment to keep the users hands away from what he is cutting whereas the slight extension before the curve is for putting your thumb on for more control. The owner, Mr. Sagen got it razor sharp with river stones before I purchased it. Performed very well so far, good weight on the end so I can chop down on things easily.
The half-sheath is designed to aid cleaning the insides so it does not jam up like how some full sheathed parangs do over time or lack of cleaning before putting it back into the sheath.
For more insights and interesting article's check out bandel4's site:http://www.my-rainforest-adventures....v-1/#more-1617
There is a picture of Mr.Sagen holding my parang.