Fictional language is a device used by authors to underline differences in culture by having their characters communicate in a fashion which is both alien and dislocated. Primary examples of this are
George Orwell's
Newspeak in
1984, [Ursula K LeGuin]
?'s Pravic
? in
The Dispossessed and [Anthony Burgess]
??'s Nadsat? in
A Clockwork Orange.