This English expression is used much more commonly in American English as this is where it has its roots. It is however used in British English as an “imported expression” from the US.
The expression is used to mean that everything which could have been done has been. Generally if someone is told that they have “gone the whole nine yards” it is taken as a huge compliment and means that this person has really pulled out all the stops and has left no stones unturned.
There is no consensus on the origins of this expression but the first recorded usage dates back to 1906 in a copy of the Indiana newspaper The Mitchell Commercial which wrote “The regular nine is going to play the business men as many innings as they can stand, but we can not promise the full nine yards.”
It is suggested that the expression is linked to World War II and the fact that aircraft machine gun belts were 9 yards in length and thus “going the whole nine yards” meant to do everything possible and use up all possible resources in order to beat the enemy.
An example of this expression can be found in Elaine Shepard’s Vietnam War novel The Doom Pussy, published in 1967. The quote reads “slipping out of the knot was expensive but Smith was eventually able to untangle what he called the whole nine yards.”