Algonquian is one of the largest language families in North America, running from the Atlantic coast to the Rocky Mountains and from Labrador to North Carolina, and it includes Cree, Ojibwe, Blackfoot, Miqmaq, Innu, Lenape, Shawnee, Arapaho, Cheyenne and many others. Lyle Campbell's survey of the historical linguistics of native North America sets out the family and the reconstruction of Proto-Algonquian, which is one of the best established proto-languages anywhere outside Indo-European, worked out in detail because the daughter languages are numerous and well recorded.
The word manitou comes from this family and has been carried into English with most of its meaning stripped out of it. In the languages themselves it refers to spiritual power, or to a being holding such power, and the Ojibwe compound that missionaries took up for God did not originally name a single supreme deity. That translation is a good example of the wider problem, because a great deal of what is written about Algonquian religion is written in vocabulary shaped by the people who were replacing it, and the shape survives in the sources long after the intention behind it has been forgotten.
The peoples in this family hold distinct religions with their own ceremonies, societies and restrictions, and the atlas treats them under their own names rather than as a single tradition that happens to share a grammar.