Of course, I always ask, "how does a word make it to the dictionary?"
Many of these words have been around for a while. (In fact, Merriam-Webster traces ginormous back to 1948, when it appeared in a British dictionary of military slang!) However, just because a word is used, doesn't mean it will make it into the dictionary. Editors who work for the dictionary spend a few hours each day reading magazines, newspapers, and electronic publications, checking for new words or variant spellings of existing words.
If they find a word of interest, they will write a citation for it. Later, definers go through the citations and decide which words should be included. It doesn't matter how often a word is cited, because it may only be found in very specific writings (like only scientific journals or only rap lyrics). To be included in a Merriam-Webster dictionary, a word must have a number of citations that come from a many different types of writing over a long period of time. The word must be used long enough and in enough variety such that the word's meaning is clear.
The number and type of citations needed to add a word to the dictionary varies. In some cases, a word comes on fast and widespread, and its meaning is clear and uncontroverted. This was the case in the 1980s with the word AIDS. In such a situation, the editors may decide to include the word, even though it has not been in use for a long period of time.Still interested? There's even a "new word watch" blog! (Scroll down to view most recent posts.)