There are many theories about who Theophilus is; the person to whom Luke writes his gospel and the Atcs of the Apostles. The most obvious answer may be right under our noses.
Theo means God. Phila means friends. It is written to God’s friend.
it is written for us.
Ex 33:11 The Lord spoke with Moses face to face, just as a man speaks with his friend.
at Last Supper Jesus says I call you friends (need citation)