I would like to ask about the ruling on naming someone Fidaa Al-Din.

Some scholars disliked naming with any name appended to the word "al-Din" (religion) or "al-Islam," such as "Nur al-Din" (Light of the Religion) or "Izz al-Islam" (Glory of Islam), because the listener might mistakenly think it is an attribute of the named person. Imam al-Nawawi explicitly stated that it is not permissible for someone to be given the epithet "Muhyi al-Din" (Reviver of the Religion). This dislike is a dislike of tanzih (discouragement without prohibition), and it is better to name with names that signify servitude to Allah or with well-known names, such as Abdullah, Muhammad, and Omar.