I have found the various Gazetteers to be fun reading but much of what they contain was collected by bureaucrats and "local informants" who were not necessarily the most reliable or best informed individuals. Thus, the names they provide for tribal/ethnic groups are often poor transliterations of the local names. It becomes hard to identify who they are talking about, and that's what I think is happening here. Burma was some distance from the Colonial administrative headquarters in Delhi and I suspect that the greater rigor of reporting found in the Indian Gazetteers may not have carried over to the Burmese reporting. I have similar issues with some of the reports coming from the NE Indian frontier, including Assam and its neighbors.
One book on the Kachin that I have found reasonably thorough in its approach (although racist and condescending) is The Kachins: Their Customs and Traditions
by O. Hanson (1913). Hanson attempts to trace the origins of the Kachin geographically and how the Kachin name arose. The Kachin call themselves Jingphaw in Burma (Singphaw in Assam), and have no knowledge of the origin of the word "Kachin" other than it appears to be a Burmese term applied to them. Hanson speculates on its origins from Chinese and Burmese sources.
The book is quite detailed in its descriptions of culture and customs of the Kachin. There is relatively little, however, about the Kachin dao
. I did find these passages helpful:
The only articles common to the men of today [i.e., in 1913] is the long, useful sword and the equally indispensable bag or haversack. No man is ever seen without these necessities. The true Kachin sword is now rarely seen south of Myitkyina and Mogaung. The Shan article is in common use. ... (p. 47)
...All his hardware comes from the Chinese or Shans, except that some of the Hkahkus make, what may be called, the genuine Kachin blades. These are about eighteen inches long, broadening from the handle outward. They are never pointed, as is the Shan dha. There are at least four varieties, of which one with clear, wavy streaks of steel running down the blade, is the most valuable and appreciated. This sword was carried by chiefs and persons of importance. They are now hardly ever seen south of Myitkyina and Mogaung, while only a few years ago they were not uncommon south of Bhamo. The Shan product is cheaper, if not so durable, and the Hkahkus do not come south, as they formerly did, to dispose of their wares. ... (p. 72)
As to who the Hkahkus were, Hanson is quite specific:
... As it often happens that the conquerors are intellectually conquered by their subjects, so too it has happened here. The Kachins that remained on the west side of the Irrawaddy developed localisms in their speech, and many of them, as in the Hukong and Kamhti valley, became strongly influenced by the Shans as to customs and religion. ... This is especially true of the Assam Kachins and those of the Hukong. The more isolated communities in the hills also developed some special characteristics and peculiarities in dialect. Those along the west bank of the Irrawaddy in time became known as the Hkahku, that is, the "up-river people." Their dialect differs somewhat from ordinary Kachin (Jingphaw), but they are true Kachins and adhere strictly to the ancestral customs and traditions. ... (p.24) (underlining is mine)
According to Hanson, the traditional Kachin dao
was made primarily by the Hkahku, a true Kachin tribal group, who were influenced by Shan culture. Presumably they learned some of their metalworking skills also from the Shan, but produced distinctly different swords.