Slang forms a significant part of the English language. The first slang dictionary appeared over 300 years ago, recording terms that are now mostly obsolete. Some of the old favourites survived though, and a few were thought too vulgar to include in standard dictionaries until quite recently.
"The Vulgar Tongue,"
Word Ways: Vol. 41
, Article 9.
Available at: http://digitalcommons.butler.edu/wordways/vol41/iss2/9