The whole shebang
All of it; the whole thing.
This is an American phrase, from the 1920s. The first question for those of us not living in the USA, and I suspect quite a few that do, is, what's a shebang? That isn't so easy to answer. The earliest known citation of the word uses it as some form of hut or rustic dwelling. That's in Walt Whitman's Specimen Days, from Complete Poetry and Collected Prose, 1862:
"Besides the hospitals, I also go occasionally on long tours through the camps, talking with the men, &c. Sometimes at night among the groups around the fires, in their shebang enclosures of bushes."
Some have speculated that there might be a connection between 'shebang' and the Irish word 'shebeen', which has a similar meaning to the 'rustic dwelling' above. There doesn't seem to be any justification for that though and the words' similarities appear to be just coincidental. Just a few years after Whitman's poem, the Marysville Tribune, November 1869 printed a list of 'The Idioms of Our New West' and defined 'shebang' like this:
"'Shebang' is applied to any sort of house or office."
Soon after that, Mark Twain uses 'shebang' to refer to a form of vehicle - in Roughing It, 1872:
"Take back your money, madam. We can't allow it. You're welcome to ride here as long as you please, but this shebang's chartered, and we can't let you pay a cent."
There are various 'the whole' expressions which derive from America - 'the whole ball of wax', 'the whole nine yards', 'the whole box of dice', 'the whole shooting match', 'the whole enchilada', 'the whole kit and caboodle' etc. Whilst these by and large refer to real objects, none of them represents 'wholeness' and they have just been tacked on to 'the whole' to make catchy phrases. 'Shebang' was also used that way - and that the fact that people using it didn't know what a shebang was didn't really matter. It was simply a colourful way of saying 'thing'.
The word appears to have arrived fully formed in the 1860s. Prior to 1862, there are no examples in print. During the 1860s there are dozens of examples in US newspapers, literature etc.
That 'vehicle' usage does suggest a possible link with the name for a form of early UK sightseeing bus, i.e. charabanc (pronounced sharra-bang). This derives from the French char-à-bancs - carriage with benches. Charabancs, affectionately known to passengers as 'sharras', were a commonplace in Britain from the introduction of horse-drawn examples in the early 1800s to as late as the 1970s.
Could 'shebang' be a variant of 'sharra-bang'? Well, it's certainly possible, although the evidence to support that view is entirely circumstantial.
In June 1872, the same year that Twain was using 'shebang' to mean vehicle, the Sedalia Daily Democrat printed a piece which used the name just to mean 'thing', and this is the earliest example of 'the whole shebang':
"Well, the Democracy can flax [beat up] the whole shebang, and we hope to see our party united."
See other phrases that were coined in the USA.