My sister is horrified by my use of the word "ginormous." You're an English major, she cries. You can't use that word! I have to admit, I heard the word quite a bit before I let it enter my regular vocabulary. And I really don't use it that often. But sometimes it really is the perfect word -- like for these ginormous knitting needles that I just bought.
Although I don't know for sure, my guess is that "ginormous" appears in the soon-to-be-in-paperback Slam Dunks and No-Brainers: Pop Language in Your Life, the Media, and Like . . . Whatever. The book, by Leslie Savan, a Pulitzer finalist, is a review of "pop" language and how it affects our communication and our thinking.
But back to "ginormous" (a combination of gigantic and enormous): Per Tim, over at Mother Tongue Annoyances, the word has been in use since the mid-20th century, possibly of World War II origin. It's known as a portmanteau: two words combined to make a new word (e.g., smoke and fog to make smog). Last year, "ginormous" topped the list of words people most wanted to see in a dictionary.
Now you want to talk really made up words? Try this exchange from The Simpsons episode "Lisa the Inconoclast." Upon hearing Springfield's motto, A noble spirit embiggens the smallest man, Mrs. Krabappel responds that she's never heard the word "embiggen." "I don't know why," answers a colleague, "it's a perfectly cromulent word." (Check out this link to Wikepedia's list of Simpsons neolgisms.)
"Cromulent," in particular, has been picked up by Simpsons fans and gained a life of its own. So much so that it's now even listed in Webster's New Millenium Dictionary. Sigh. I don't have the heart to tell my sister.