cottonmouth

The word is a transparent English compound, formed by combining two common nouns. The first element, 'cotton', is a loanword ultimately from the Arabic 'quṭun', which entered English via Romance languages to denote the soft white fibrous substance. Its use here is purely metaphorical, drawing a visual analogy to the distinctive white interior of the snake's mouth, which it displays as a warning. The second element, 'mouth', is a native English word from Old English 'mūþ', of Germanic origin. The compound's literal meaning, "a mouth resembling cotton in color and texture," perfectly captures the defining characteristic of the Agkistrodon piscivorus snake, leading to its primary zoological definition. The secondary sense, "dryness of the mouth," is a later figurative extension, playing on the sensation of having a mouth as dry as cotton.

Structure: cotton + mouth - cotton (English, from Arabic via Romance languages): In this compound, it functions as a descriptive element, evoking the soft, white appearance of the cotton plant's bolls. - mouth (Old English): Functions as the core noun, denoting the oral cavity of an animal or person.