The phrase "debt of honor" refers to a moral obligation that one has towards another. It is often used in discussions of loyalty, integrity, and honor. Some synonyms for "debt of honor" include "moral obligation," "duty," "responsibility," and "commitment." Other related terms may include "loyalty," "integrity," and "honesty." However, each of these terms may have a slightly different connotation or emphasis, so it is important to consider the context in which they are used. Overall, the concept of a debt of honor highlights the importance of maintaining strong moral principles and ethical behavior, even in difficult situations.