Why did Anthony Burgess use so many made-up words when writing A Clockwork Orange?
A Clockwork Orange is a dystopian work set in the near-future, and so it involves a specific sort of future slang created by Anthony Burgess. He based his slang terms on rhyming slang, which is common England, where Burgess lived; a linguist, Burgess also introduced Russian terms. He called his created slang Nadsat, and intended it to create a modern-sounding dialect that would remain fresh. Since language changes over time, using contemporary terms would have caused the book to feel dated after several years. Nadsat always looks unusual, and therefore both reinforced the concept of a living future, and prevents the book from sounding like a product of 1960s England. The language is commented on by the better-educated doctors while Alex is being studied:
"These grahzny sodding veshches that come out of my gulliver and my plott," I said, "that's what it is.""Quaint," said Dr Brodsky, like smiling, "the dialect of the tribe. Do you know anything of its provenance, Branom?""Odd bits of old rhyming slang," said Dr Branom, who did not look quite so much like a friend any more. "A bit of gipsy talk, too. But most of the roots are Slav. Propaganda. Subliminal penetration."
(Burgess, A Clockwork Orange, Google Books)
Alex's sentence in the above quote would translate to mean: "These [dirty] [expletive] [things] that come out of my [head] and my [body]." Dr. Branom comments on the propaganda roots of the Russian, indicating the intrusion of Communism into popular culture. Since Nadsat is not a slang form used in the real world, it can be seen as an entirely unique language form. The book's writing thus feels more fresh and original, instead of sounding like it is set in the era of its writing.
Another reason Burgess used a constructed slang in A Clockwork Orange is that he was an ardent scholar of James Joyce, and specifically of his work Finnegans Wake. He wrote on Joyce's work several times, including the books Joysprick, Re Joyce, and A Shorter Finnegans Wake, in which he tried to simplify Joyce's book. In using Nadsat to write A Clockwork Orange, Burgess is emulating Joyce's groundbreaking use of language to condense the meaning of several words or historical references into single words or short phrases.
Like Joyce, Burgess brings in complexity by his word structure, pulling in several meanings at once. For example, the word "horrorshow" in Nadsat means "wonderful," and while it's based on the Russian word "horosho" meaning "good," it also evokes the English phrase "horror show," which would carry the opposite meaning for most of us. However, it also expresses Alex's perverse viewpoint, since he actually likes many things that would repulse most people. Therefore, it expresses the Russian influence and produces a semantic tension for most readers by juxtaposing its usage with its surface meaning, while also expressing Alex's twisted nature, all at once.