A more thorough explanation:

dilecto et fideli (di-lek-toh et fi-dee-lI). [Law Latin] To his beloved and faithful. This phrase was used in various writs. Abbr. di. et fi.

The term dilecto et fideli is a Latin phrase that was commonly used in legal documents. It means "to his beloved and faithful." This phrase was often used in writs, which are legal documents that authorize a person to take a specific action.

• A writ of habeas corpus might begin with the phrase "To his beloved and faithful sheriff, greeting."
• A writ of execution might begin with the phrase "To his beloved and faithful bailiff, greeting."

These examples illustrate how the phrase dilecto et fideli was used in legal documents. It was a way of addressing the person who was being authorized to take a specific action, such as arresting someone or seizing property. By using this phrase, the writer of the writ was acknowledging the trust that was being placed in the person who was being authorized to act.