It's normally a joke.
It's 'funny' because "What can I do you for?" is actually a question that would never be asked, except rhetorically.
Do you, as in "I'm gonna do you in" is what a thug would say before he perpetrated violent acts against you. It could also be used by a police man, for example "Do him for possession", so do him is slang for arrest him.
There is also, the more pertinent definition of do you, which is what a swindler would think when tying to think how to trick you: "What can I do you for?" Where what they mean is "What can I get out of you with my tricks?"
Whereas "What can I do for you?" is someone simply asking how they can help. In the context of a barman, it would be asking what drink or other pub service they can provide.
GrammarGirl did a whole post on this. She explains that there is a difference between between and among. She writes:
Here's the deal: you can use the word “between” when you are talking about distinct, individual items even if there are more than two of them. For example, you could say, "She chose between Harvard, Brown, and Yale" because the colleges are individual items.
She goes on to explain that in the following cases, you use the two slightly differently:
Relationships: The Chicago Manual of Style describes these as one-to-one relationships. Sometimes they are between two items, groups, or people, as in these sentences:
- Choose between Squiggly and Aardvark.
- Let's keep this between you and me.
Other times they can be between more than two items, groups, or people as in these sentences:
- The negotiations between the cheerleaders, the dance squad, and the flag team were going well despite the confetti incident.
- The differences between English, Chinese, and Arabic are significant.
On the other hand, you use “among” when you are talking about things that aren't distinct items or individuals; for example, if you were talking about colleges collectively you could say, "She chose among the Ivy League schools."
If you are talking about a group of people, you also use “among”:
Part of a Group:
“Among” can also indicate that someone is part of a group or left out of a group, as in these examples:
- He was glad to find a friend among enemies.
- She felt like a stranger among friends.
- Sylvia was later found living among the natives.
From this, you were correct in your use of between. "Cook et. al." formed part of a distinct group of individuals, so you would use between.
Best Answer
This is similar to the relation between “while” and “whilst”, or between “amid” and “amidst”.
As with "whilst", "amongst" is:
chiefly British
"while using whilst runs the risk of sounding pretentious, it can sometimes add a literary or ironically formal note to a piece of writing" [American Heritage Guide]
"The general consensus among scholars of English is that whilst is an unnecessary and archaic word whose primary usage is by Britons who prefer what they perceive as a more 'noble' word" [Strunk and White]
recommended against by Times Online Style Guide: "amid, not amidst; similarly among, not amongst", by the Guardian Style Guide: "among not amongst", and by [Hansard Association of Canada]: "among (no -st)". And some Tameri Guide says: "among / amongst - In American English use among to mean within a group. Amongst is antiquated for in the middle of a situation or gathering."
Anyway, the summary seems to be that "amongst" is slightly pretentious (or "distinguished" as you say), but is common in Britain, and its meaning is almost identical.