The term 'swearing-in words' refers to the words used in a formal ceremony to swear an OATH of office. The most common swearing-in words are 'OATH' (4 letters), 'OATHS' (5 letters) and 'I do' (3 letters). An OATH is a solemn promise to be honest and faithful in the performance of one's duties. OATHS are often taken by public officials, such as presidents, judges, and members of the military, to signify their commitment to serve the people. I do is a phrase used to affirm one's commitment to an OATH.