Rob, in this discussion of a
koummya/khanjar dichotomy it may be worthwhile looking at the etymology of the two words. I think, from memory, that
khanjar is a Persian word for a double-edged, curved dagger (1). And from there, the name was adopted and used throughout the Ottoman Empire (extending into the Middle East and Arab world), and by the Moghul Empire in India.
I don't know the derivation of
koummya. The knife is, of course, a double-edged, slightly curved dagger found in Morocco and other parts of the Magrib. The term appears to apply just to a particular style of dagger that is relatively localised in manufacture. The term
khanjar was used more widely in the Persian, Indo-Persian, Ottoman and Arab worlds to describe a range of double-edged, curved daggers.
I think one could consider the
koummya as another regional type of
khanjar that is found in the Magrib. That other types of
khanjar might be found in the same area is not surprising. When we talk about a family of similar weapons, there are two schools of thought: the "lumpers" and the "splitters." The "lumpers" look at similarities that share a common theme and use; the "splitters" see subtle differences that may reflect national/ethnic/political distinctions, and believe these differences are important. For the most part, I'm an unashamed "lumper" who appreciates the subtle differences in style (and local passions about ownership), but in the final analysis these are essentially similar weapons.
(1) See
Peter Dekker's page for a scholarly discussion.