Nawathinehena is an extinct Algonquian

Algonquian languages

The Algonquian languages also Algonkian) are a subfamily of Native American languages which includes most of the languages in the Algic language family. The name of the Algonquian language family is distinguished from the orthographically similar Algonquin dialect of the Ojibwe language, which is a...

 language formerly spoken among the Arapaho people. It had a phonological development quite different from either Gros Ventre

Gros Ventre language

Atsina is the moribund Algonquian ancestral language of the Gros Ventre tribe in Montana. The last fluent speaker died in 1981. Atsina is the name applied by specialists in Algonquian linguistics...

 or Arapaho proper

Arapaho language

The Arapaho language or hinono'eitiit is a Plains Algonquian language spoken almost entirely by elders in Wyoming, and to a much lesser extent in Oklahoma. It is in great danger of becoming extinct. As of 1996, there were approximately 1,000 speakers of theNorthern Arapaho...

. It has been identified as the former language of the Southern Arapaho, who switched to speaking Arapaho proper in the 19th century. However, the language is not well attested, being documented only in a vocabulary collected in 1899 by Alfred L. Kroeber

Alfred L. Kroeber

Alfred Louis Kroeber was an American anthropologist. He was the first professor appointed to the Department of Anthropology at the University of California, Berkeley, and played an integral role in the early days of its Museum of Anthropology, where he served as director from 1909 through...

 from the Oklahoma Arapaho. Among its divergent features is the appearance of Proto-Algonquian */s/ as /t/.