Little of the Susquehannock language has been preserved. The only source is a Vocabula Mahakuassica compiled by the Swedish missionary Johannes Campanius during the 1640s and published with additions in 1702. Campanius's vocabulary contains only 89 words but is sufficient to show that Susquehannock was a northern Iroquoian language closely related to those of the Five Nations. Surviving remnants of the Susquehannock language include the river names Conestoga, Juniata, and Swatara.
^Thomas Campanius Holm. 1702. A short description of the province of New Sweden, tr. Peter S. du Ponceau. Pennsylvania Historical Society Memoirs 3:1:1-166. (Reprinted 1834 in Philadelphia)
cited in Marianne Mithun. The Languages of Native America (1999, Cambridge University Press).
^Marianne Mithun. 1981. "Stalking the Susquehannock," International Journal of American Linguistics 47:1-26.