A booger of collective nouns

I am reading a book in which a character mentions that a group of ravens is called an "unkindness." This got me thinking of the preponderance of wacky collective nouns out there . . . how were they chosen, and why not just keep it simple and call a group, a group? I don't have an answer for the former (do you?), but my guess in the latter is that "group" is simply not as fun.

Many of the more interesting collective nouns are reserved for birds. To name a few:

• storytelling of rooks
• murmuration of starlings
• wedge of swans
• descent of woodpeckers
• skein of goslings (which grow into a gaggle of geese)
  
• piteousness of doves
• ostentation of peacocks
  

There was a segment on the CBS Sunday Morning Show about collective nouns, but I can't find a link for it. A Google search did point me to the Fun With Words site, which includes a lengthy list of collective nouns specific to animals. Here are a few of my favorites from that site (although I must say I don't know if I believe all of them):

• prickle of hedgehogs (how descriptive!)
  
• sneak of weasels (invented, I am guessing, by an angry chicken farmer)
  
• hurtle of sheep (invented, I am guessing by a BORED sheep farmer)
  
• smack of jellyfish (I would have chosen "sting," but okay)
  
• cartload of monkeys (I'm not buying it--but I like it!)
  
• shrewdness of apes (Jane Goodall would approve)
  
• movement of moles (the sheer alliteration gives me joy)