The name for this river was mentioned as early as 1904 by the Dominion Lands Survey which went through the area that year. It has been stated in a number of sources that "Assineau" is a rendering of the Cree word meaning "nobody." Yet another source has translated the word to mean "stony." G.M. Dawson in 1879 transcribed the Cree word for people as ai-si-ni-wok. According to another source, the Cree for nobody is namawiyak. Other references have been made to it as "Sinew River."

Flows north into Lesser Slave Lake approximately 29 km west north-west of Slave Lake.