You are not allowed to name your Guardian Angel. Some Catholics practice a devotion of giving personal names to their guardian angels. However, the Holy See does not allow this practice and formally discourages it.
According to the Directory on Popular Piety and the Liturgy, 216 (under the heading about Devotion to the Holy Angels):
The practice of assigning names to the Holy Angels should be discouraged, except in the cases of Gabriel, Raphael and Michael whose names are contained in Holy Scripture.
A special thanks to Father Gary Selin and my friend Jordan Low for finding this citation.
What’s the Theology Behind Not Naming Your Guardian Angel?
We cannot name our Guardian Angel because naming another implies authority over the other. I name my children and I name my pets. I have authority over them.
However, my Guardian Angel is OVER me in authority:
Angel of God my Guardian Dear
to whom God’s love commits me here
Ever this day be at my side
To light, to guard, to *RULE,* to guide.
Therefore, I do not have the authority to name my angel. My angel is not my dog, he’s my instructor.
When God gives a new name to someone (Abraham, Israel, Peter), he is signifying His authority over him as that person acts as His vicegerent in His name. Notably, God revealed the names of Jesus, Mary, and John the Baptist to their parents before they were born to show His special authority in human redemption.
Please share this post on Facebook and Twitter, since most people still think it’s alright to name their angels. We need to get the word out.