the.com/water moccasin

means A venomous, semi-aquatic pit viper of the southeastern U.S. wetlands, also called a cottonmouth for the pale, gaping lining of its mouth it flashes as a warning.

from The 'moccasin' half likely comes from the snake's dull, mottled brown-and-olive banding, which struck early English-speaking settlers as resembling the leather of Native American moccasins — an association with Indigenous dress rather than a word borrowed from any specific Native language. 'Water' simply marks it off from its dry-land cousin, the copperhead, since this one hunts and suns itself in swamps, rivers, and ditches rather than woodland leaf litter.