A-ca-oo-mah-ca-ye

Aka-Omahkayii (also Ackomokki or A-ca-oo-mah-ca-ye (Blackfoot syllabics: , meaning Old Swan), was the name of three Siksiká chiefs between the late 1700s and 1860.

Aka-Omahkayii/Old Swan (I) The first Aka-Omahkayii was described by Duncan M'Gillivray, the North West Company clerk at Fort George, as "once the greatest of this Nation and was respected and esteemed by all neighboring tribes." By the time Aka-Omahkayii was chief, the Blackfoot/Plains Confederacy had consolidated power throughout he plains of what is modern-day Montana, Alberta, and western Saskatchewan. He was known as a peacemaker who was open to trade with Europeans. As he grew older, Aka-Omahkayii was forced to step aside as chief, but he remained a respected elder of the tribe until his death following a fall in 1795. The elder Aka-Omahkayii's retirement led to a dispute over the tribe's leadership between the younger Aka-Omahkayii and Big Man/Gros Blanc (O-mok-a-pee), who struck a more hostile position toward white traders and other Native American tribes. Despite his early success as a warrior and hunter, younger Aka-Omahkayii adopted his father's policies and worked to preserve peace among his people and the neighboring Cree and Assiniboine peoples, as well as with European traders. By contrast, Big Man was openly hostile to other tribes and European traders, going so far as to participate in the 1793 Gros Ventre attack on the Hudson Bay Company's Manchester House.

In 1800, Aka-Omahkayii allowed the Hudson's Bay Company to establish the Chesterfield House trading post within the Blackfoot's wintering grounds at the confluence of the Red Deer and South Saskatchewan Rivers. By 1810, Aka-Omahkayii was recognized as leader of at least 60 percent of the Siksiká. However, changes in the balance of power between the Blackfoot and neighboring tribes brought on in part by westward expansion of U.S. traders lead to increasing conflicts and military decline for the Siksiká. Aka-Omahkayii's maps included significant details about the topography and inhabitants of the area, which proved helpful in expanding the Hudson's Bay Company activities in the region. The following year, Fidler collected from Aka-Omahkayii a second map of the region that included pictographs marking summit features, for example a heart marking Heart Butte in the Lewis Range.

In October 1814, Hudson Bay Company trader James Bird reported that Aka-Omahkayii had been shot and killed by "a man of their own nation but of another Tribe," likely a Kainai or Peigan.

Aka-Omahkayii/Old Swan (III) A third Old Swan , possibly a son or nephew of the younger Aka-Omahkayii, assumed leadership of what was called by Europeans "Old Feathers' Band" by 1822. He was described in 1858 by Dr. James Hector as one of the three principal chiefs of the Blackfoot Confederacy (the other two being Crowfoot and Na-to-sa-pi ), and, in July 1859, the Palliser Expedition were guests at his encampment on the Red Deer River.