It is called a service ace!
There ISN'T anything called a "backhand serve" in tennis.
If the player is unable to hit the serve then it is an ace. But if the player hits the ball but does not return it, then it is a forced error.
Because you hit the ball with some kind of racket and that is why you call it a serve.
The legal serve where the opponent fails to touch the tennis ball is called 'ACE'.
No. The interior lines (half-lines) on tennis courts determine the service court, into which the serve must be made. An ACE is any legal serve that is not successfully returned by the opponent, winning the point for the server.
I (believe) that it is because you give the ball to the other halve of the court, as if you are their waiter and are serving them.