Blood: from the Battle of Blood River, where 600 voortrekkers fought off 20,000 attacking Zulu troops. No voortrekkers were killed, but the dead Zulus (3,000 died) stained the nearby river with blood, and so the name stayed.
Bow: After the reeds growing along its banks, which were used by the local Indians to make bows.
Brazos: From the Spanish Los Brazos de Dios, or "the arms of God". There are several different explanations for the name, all involving it being the first water to be found by desperately thirsty parties.
Canadian River: The etymology is unclear. The name may have come from French-Canadian traders and hunters who traveled along the river, or early explorers may have thought that the river flowed into Canada.
Snake River: Derived from an S-shaped gesture the Shoshone made with their hands to represent swimming salmon. Explorers misinterpreted it to represent a snake, giving the river its present-day name.
Bright, William (2004). Native American Place Names of the United States. Norman: University of Oklahoma Press
Blažek, Václav, and Ondřej Šefčík. "Oronyms Derived from Water? Mons Abnobae and Haraitī". Historische Sprachforschung [Historical Linguistics] 124 (2011): 239–49. http://www.jstor.org/stable/41553574.
Hamp, Eric P. ""Water" in Italic and Keltic". In: Etudes Celtiques, vol. 12, fascicule 2, 1970. pp. 547–550. DOI: https://doi.org/10.3406/ecelt.1970.1436 ; www.persee.fr/doc/ecelt_0373-1928_1970_num_12_2_1436