Once upon a long time ago in France, there was the word étiquette. But it didn't have the meaning that it has today. Etiquette was nothing to do with passing the port the right way through a revolving door. An étiquette was just a small piece of paper.
So far as anybody can tell (and nobody is sure of this) people would write down the rules of the court on a small piece of paper and hand them out to visitors, or pocket them so they didn't forget who was meant to give way to whom. Thus our English etiquette.
However, the primary French sense also got straight into our language by the much simpler route of dropping the E at the beginning. Etiquette became ticket: train tickets, political tickets, lottery tickets. Even the small piece of paper behind the bar on which your drinks bill is tallied is a ticket. That's why, when you buy something on credit, you buy it on tick.
Court etiquette used to be a terribly complex and time consuming thing. For example, when you got up to leave from supper everybody had to leave in reverse order of seniority, with the king going last. That meant that you had to size up everybody else at the table and shuffle around and wonder whether it was your turn (unless you slyly consulted your étiquette) and it all got very awkward and slow. That's why when Lady Macbeth tells her dinner guests to leave immediately, she says:
At once, good night:
Stand not upon the order of your going,
But go at once.
The order there isn't her command, it's about not standing on ceremony and just Getting Out Now.