The term 'four-letter words' refers to words that are composed of four letters. One example of a four-letter word is 'OATHS', which is a promise or statement of intent made by one person to another. OATHS are often used in legal contexts, such as when taking an oath in court or swearing an oath of office. OATHS can also be used in more informal contexts, such as when making a promise to a friend or family member.