The Arabs before Islam used to begin their works by naming their gods, saying “By the name of al-Laat” or “By the name of al-Uzzaa”. Other nations used to do the same. If one of them wanted to do something to please a king or ruler, they would say it is done “by the name of” that person, meaning that this deed would not be if it wasn’t for that king or ruler.
For this reason, when you say “I begin my deed with bismillah al-rahman al-raheem” (in the name of God, Most Gracious, Most Merciful), it means “I am doing it by God’s command and for His sake, and not for the sake of my ego and its pleasures.
Shaykh Ahmad Mustafa al-Maraghi, Tafseer al-Maraghi.