The term 'courtroom promise' is a phrase used to describe the solemn promise made by a witness in a court of law. The two crossword solutions for this term are 'OATH' and 'IDO'. OATH is an acronym for 'I Do Solemnly Swear', which is a phrase commonly used in courtrooms when a witness is making a promise to tell the truth. IDO stands for 'I Do', which is another phrase used to signify a witness's promise to tell the truth.