Word salad for instance, “Colorless green ideas sleep furiously”, where phrases are grammatically correct but have no known meaning is a feature of mental illnesses such as schizophrenia and dementia. Word salad is so named to highlight the apparently random mixture of words that resembles the random mixture of vegetables, fruits, meats, etc. in a salad - word salad.
Schizophrenia is a psychiatric disorder that is difficult to define and describe, however some of its features include delusions, hallucinations and interference with speech and thinking which lead to significant social and occupational dysfunction. Delusions are fixed false firm beliefs unaltered by evidence to the contrary e.g. that everyone in the world is watching one; a hallucination is perception without a stimulus e.g. hearing voices of dead people giving one instructions; interference with speech and thinking e.g. word salad.
Dementia is not a single disease but a state characterized by overall impairment of intellect, memory and personality without loss of conscious that can be caused for example by infection, trauma, toxins, cancer, and so on.
Noam Chomsky (born 1928) an American intellectual originated the above quoted sentence for illustrative purposes.
Portnoff LA. Schizophrenia and semantic aphasia: a clinical comparison. Int J Neuroscience, 1982 16(3-4):189-97. Go to reference