This thread has been fascinating - Jim, you are an encyclopedia of knowledge.
As has been mentioned, the axe form seems to be ubiquitous to Central Africa, appearing in one variation or another across a large swath of the continent. However, (some of) the embellishments are distinctly Arab in nature, leading to some speculation to a possible Omani origin - or at least Omani influence - vis-a-vis the Omani jurisdiction over Zanzibar.
I read with interest the mention of Tippu Tib and the Arab traders who penetrated deep into the interior of Africa from Zanzibar to the west (it should be noted these trade routes also extended southward from Gondokoro along the Upper Nile to the north).
When Stanley led the 1887 expedition to "rescue" Emin Pasha (a.k.a., Eduard Schnitzer), the successor to Charles Gordon as governor of Equatoria (lower Sudan), Tippu Tib accompanied them from Zanzibar with an entourage of 97 people, including traders, porters, and his harem.
However, of note is the route this expedition took. They did not travel eastward from Zanzibar westward across Tanzania. Rather, they sallied around the Cape of Good Hope and up the west coast of Africa to the mouth of the Congo River (
no.1 on the map below), and mounted their expedition up the Congo, traveling
east.
Tippu Tib had agreed to accept the offer of Belgian King Leopold II (and delivered by Stanley) to become the governor of the Stanley Falls district (
no. 3 on the map below) of the Congo Free State (CFS), the Belgian mercantile colony that ran the length of the Congo River from the Atlantic to the Ituri Forest. As per his agreement and charter, he would be allowed to manage the trade from Stanley Falls, and to exploit local resources in the neighboring areas adjacent to his district, provided they were not part of the CFS.
When the expedition landed at the village of Yambuya (
no.2 on the map below), they set up a fortified camp from where the main body of the expedition would travel overland through the Ituri Forest for the remainder of the trip. They averaged about five miles a day, and just three days out from Yambuya encountered trail markers belonging to other Arab slave traders.
In short, not only was the self-appointed "king" of the "Arab"
* slave traders active in the heart of the Congo, but other Arab traders were also active in the area. The activity of these traders and the resulting sphere of interaction actually extended much further than Lake Tanganyika to the east, and thus, given the Islamic influence to the northwest and the accompaniment of Tippu Tib and his entourage from the mouth of the Congo River, the possible origin of the axe should IMO be considered to include pretty much the entirety of Central Africa.
*The terms "Arab" and "Turk" were used by Africans to describe any number of ethnographic peoples of mixed Turkish, Arab, and African descent who populated a wide region from Zanzibar in the west to the Sudan and Egypt to the north. Tippu Tib, for instance, was born to an Omani mother and a Swahili father.
