I wonder where that name came from. One of the books of Thap religion, written by Dara stated that it is a divine song from god. 'Geeta' means song in Sanskrit. So the name of the book is Gita.
Do you know any other reason why this name was kept?
Gita is called gita, because it is the devine song by god. Song is called Geet in sanskrit, from where the name came. It is very interesting and good to know.