Nadsat is a fictional argot which exists in Anthony Burgess' 1962 novel 'A Clockwork Orange'. Burgess invented this language for his book because he wanted the teenagers in his story to have their own slang. The term 'Nadsat' is derived from the Russian equivalent of the sufffix '-teen'.(eg. 'thirteen' in Russian is 'тринадцать/trinadtsats' [the '-teen' part is '-надцат/-nad.tsat']) It's true that Burgess wanted the reader to be unfamiliar with the slang while they read the book & to have to figure out the meaning of the words for themselves (he especially didn't want a dictionary or glossary to be available to the reader), however, a dictionary is definitely a huge advantage in order to be able to understand what Alex (the novel's anti-hero) & his gang of troublemakers are talking about.

Nadsat is mainly influenced by the Russian language. Anthony Burgess anglicized the spelling of Russian words, while keeping the pronunciation & the meaning the same as or very similar to the Russian origin.
One example is the nadsat term 'droog'. Burgess took the pronunciation & meaning of the Russian 'друг/drug' ('friend') & spelled it like it was an English word. Alex uses the word droog to refer to his pals.

Homophones were also employed by Burgess in a few cases to create Nadsat terms. These examples appear to be a play on English words but are, in fact, of another origin. An example is the Nadsat term 'horrowshow'. This word is used to describe something which is great & enjoyable. One may easily assume that since 'horrow show' is an English term, the Nadsat word is derived from this in some way. However, it actually comes from the Russian language also. 'Хорошо/Xorošó' is a Russian word which translates into English as 'well' or 'good'. Burgess noticed the similarity between the sound of the Russian word 'хорошо/xorošó' & the English phrase 'horror show' & conjured up the Nadsat word 'horrowshow', holding the Russian sound & meaning, but English-like spelling.

Some English words were simply blended, clipped or exaggerated to make Nadsat terms, such as 'bedways' (to bed), eggiwegg (egg) & 'em' (mother).