The name LET is used because the attempt at service is not counted. As a player, you are letting the ball pass, hence the name let. The server gets a second attempt at whichever service it is, the first or the second. It can be a let first serve or a let second serve.
Beside this, what does let mean in tennis terms?
Let – a serve is called a let when the ball hits the net cord but still lands in the service court. Such a serve is not considered a fault and the server may repeat the service attempt. A ball that hits the net cord but lands outside the service box is still a fault.
Likewise, people ask, why is it 40 not 45 in tennis?
When the hand moved to 60, the game was over. However, in order to ensure that the game could not be won by a one-point difference in players’ scores, the idea of “deuce” was introduced. To make the score stay within the “60” ticks on the clock face, the 45 was changed to 40.