four-letter

The compound 'four-letter' is a straightforward Modern English construction combining the cardinal number 'four' with the noun 'letter'. Its primary literal meaning simply denotes anything composed of four alphabetic characters. However, its significant secondary meaning arose in the early 20th century as a euphemistic label for short, taboo words, primarily of Anglo-Saxon origin, which are considered obscene or profane. This association stems from the observation that many common English swear words are monosyllabic and consist of exactly four letters. Thus, the term evolved from a neutral descriptor to a socially coded reference for vulgarity.

Structure: four (number) + letter (character) - four: From Old English 'fēower', of Proto-Germanic origin, related to Latin 'quattuor' and Greek 'tessares'. Functions as a numerical quantifier. - letter: From Old French 'lettre', from Latin 'littera' (letter of the alphabet, document). Functions as the core noun denoting a written character.