You might be surprised to find out that there was a dictionary of slang published over half a century before Johnson’s mighty effort. And this year, from the bowels of the Bod, comes the republishing of The First English Dictionary of Slang, 1699.
At the time it was first published, the aim of the dictionary was to teach gentlefolk the meaning of slang words used by thieves and suchlike, should they make the mistake of wandering into a dangerous part of London.
Why is it of interest to language learners today? It provides a root and provenance for many of the slang, or slang-derived words they may find in a good learner’s dictionary. One such example given in the Bodleian article is chit-chat, an old slang word for inconsequential conversation and still a current entry in the Macmillan Dictionary.
For current slang and new words, see Macmillan Dictionary‘s Open Dictionary or Buzzword pages.

Really like ‘humptey dumptey’. If it is some sort of alcoholic drink then is the famous nursery rhyme about somone who is drunk??
What is the definitation of dandyprat?