@WW Would the same outcome apply for AmE eg Red Sox, San Francisco 49ers ,Miami Heat ??

Economy comes from Greek for houselhold management cf "oikos" meaning a house which survives as wick, wic, wich in placenames like Chiswick, Norwich, Highwic.

@WW Interesting that you say "cheeky" for (b). ESOL students sometimes use "of course" in this way with no intention of being cheeky.
I guess in some way it is payback for the implicit-in-the-question idea that the student might have been too lazy to do their homework.
But jow to ask and answer that without the side-issues?

From the following book
moly.hu/konyvek/susan-doughty-geoff-thompson-problem-english-a-practical-guide-for-hungarian-learners-of-english

"Of course: this is perfectly acceptable as a polite response to a request for information eg: Can you give me a lift? Yes of course"

"However as an answer to a request for information it normally sounds rude... eg:
Is it raining? Of course ((why do you think I'm soaking wet?))
Are you coming with us? Of course (I'm the one with the tickets you fool)

I've never been quite happy with this distinction: it seems to me that if one is continually saying "of course" it might be interpreted as betraying a contemptuous attitude.

Of course in some languages (French, German, Russian, Hungarian) the equivalent is much more common than "of course" in English, so there is a tendency for them to overuse it in English.

Or perhaps it's just all in the intonation and facial expression.

http://books.google.com/ngrams/graph?content=that+is+key+.%2Cthat+was+key+.&case_insensitive=on&year_start=1800&year_end=2008&corpus=15&smoothing=3&share=&direct_url=t4%3B%2Cthat%20is%20key%20.%3B%2Cc0%3B%2Cs0%3B%3Bthat%20is%20key%20.%3B%2Cc0%3B%3BThat%20is%20key%20.%3B%2Cc0%3B.t4%3B%2Cthat%20was%20key%20.%3B%2Cc0%3B%2Cs0%3B%3Bthat%20was%20key%20.%3B%2Cc0%3B%3BThat%20was%20key%20.%3B%2Cc0

@WW Of course.

Jasper

Of course you may do as you wish; it is indeed difficult to talk of "standard" English when discussing "thou" and "thee", and modern usage in dialects is pretty non-conformist. I tend to see KJV as being the main influence here, but of course that is fairly archaic now. There are clearly some writers out there who do not follow either KJV or modern dialect usage. Plus ca change.

Tone

Some people may use them to express annoyance or irony; others might use them because "no problem" by itself feels too abrupt.

Only real way to find out is to ask them...

(I put them here to suggest asking might be a bit tricky)

I wonder whether (if the outbound message were 'Can you send me...?' ) there would have been a more detailed answer.

Jasper

The 's' ending on the third person overtook '-th' in the late middle ages; either is possible , but '-th' is definitely archaic, and not in modern use.

My take on it would be that using "thou" without the befitting verb endings would mean the sentence was ungrammatical. The -'st' endings are still in modern use in northern England, so they are in no way optional.