A “murder” of crows. A “romp” of otters. A “sleuth” of bears. A “shrewdness” of apes. A “siege” of cranes. Full list here.
Where did all these names come from?
A lot of them were made up in England for use in witisms and fanciful writing. Scholars have tried to reproduce their lists and have since published them. Those lists have become very popular and lots of people either use them as the proper term or enjoy hearing that the collective noun for crows is a murder. In short, many of them were made up centuries ago in England for no scientific purpose.
http://home.vicnet.net.au/~rasigsau/collective_nouns_animal.htm
A lot of them come from the Book of St Albans, attributed to Dame Julia Barnes (1486).
See: http://en.wiktionary.org/wiki/Appendix:Collective_nouns
And see also: http://en.wikipedia.org/wiki/Collective_noun#Terms_of_venery_.28words_for_groups_of_animals.29
I never heard of most of the ones in that list. 
As Shagnasty mentioned, apparently many of them started as jokes. After reading Cecil’s explanation of where ‘OK’ came from (basically mid-nineteenth century leetspeak), it’s clear that one generation’s play, if it survives, can be another generation’s seriousness. (I suspect that this applies to a lot of literature, actually.)
A singular of boar?
Like Shakespeare turning from light entertainment into torture for school children.
I do think “a skulk of foxes” is appropriate. If foxes ran in groups. Which they don’t. Oh, well…
I wanted to add something the list omits:
Flock of Seagulls
Ostentation of peacocks has been my favorite for years.
2+ moose = meese?
Commonly found in that country east of Iraq.
The authoritative work on the subject is An Exaltation of Larks by James Lipton (yes, the Actors’ Studio guy, although the first edition was published in 1968, long before the show began). It’s a very interesting, engaging, and amusing book.
Contrary to what has been stated upthread, these “terms of venery” did not start as jokes. The Book of St. Albans, and many other similar works, were text books for young noblemen. The editor of a 19th century edition claimed that “at that period [the late 15th century], every man claiming to be ‘gentle’ was expected to be familiar [with the various terms]; while ignorance of their laws and language was to confess himself a ‘churl.’” So at first, knowledge of the proper terms was taken very seriously as a sign of good breeding.
However, by the 19th century it was no longer such a serious a matter, and became a sort of game.
But I suspect that the whole subject might have become nothing more than a philological footnote by now, if not for Lipton’s book. Nearly single-handedly, he resurrected the obscure old terms, rediscovered the more recent, invented a bunch of his own, and introduced 20th-century readers to the game. The book has gone through several versions, including a major new “Ultimate” edition in 1990, and has never been out of print since 1968.
You know many more of these terms than you realize. For instance, a school of fish, a swarm of bees, a bunch of grapes, a band of men, a bevy of beauties, a month of Sundays, a mountain of debt.
A flight of stairs!
And Lipton and his readers have coined hundreds of modern ones:
A brace of orthodontists
A set of mathematicians
A corps of anatomists
A sack of linebackers
A pac of video gamesters
A glut of commercials
And it just goes on and on. I think most Dopers would really enjoy An Exaltation of Larks.
As for a singular of boar, this has a rather complex and uncertain history. One possible explanation is that, after they are four years old, male wild boars go off on their own, and are never seen in groups, hence a singular. Another is that it is a corruption of the French word for boar, sanglier. Finally, Lipton points out that one of the meanings of “singular” is “extraordinary,” which seeing a group of boars certainly would be.
They have a variety of sources. Some are old Anglo-Saxon terms. The majority probably originated around the 1400s as hunting terms. Others have been made up more recently essentially as jokes.
In the 1400s they had the function of something of a social test: a gentleman was expected to learn these erudite terms related to the elite sport of hunting.
Nah. 2+ moose = fun. 
I used to date a gal who pondered: “If the plural of mouse is mice, is the plural of spouse, spice?”
And let me be the first to suggest: a teem of Dopers
A fest of Dopers, sir. A fest.
A friend of mine used to refer to “a giggle of girls”. I rather like the term. And Patrick McManus has referred to “a leap of wife”, although I think that has more to do with bills and chores.
Meeses, actually, but only if hate them to pieces.
I got that, you know.
But, Iran’s so far away.
Sorry, jayjay, but as the self-appointed local expert on terms of venery (I bought my first copy of An Exaltation of Larks back in the 1970s), I’m going to have to rule in favor of BJMoose. Very witty term, with a little inside joke for us.
Teem of Dopers it is, I hereby proclaim for all time. Amen.
pout