Was this a widely used weapon or a specialty weapon that only a few knew?

Is there a consensus that it originated in Indonesia?

The malaysians believe that the development of the karambit or what they call
the lawi ayam(chicken spur) in malaysia began with the arabian jambia which were brought
over by muslim traders to the various large islands of indonesia like Sumatra and to the
malay archipelago. It was developed into a smaller more practical concealed
weapon it seems by the Menangkabau and spread accordingly. There are various sizes and distinct features to many of the karambits. Draeger mentions that the karambit of Sumatra draws it influence as well from
the Jambia.

I'll dig into the Draeger book. Thanks for the info. and pointer.