A neologism (pronounced /niˈɒlədʒɪzəm/); from Greek νέος (neos 'new') + λόγος (logos 'speech')
In psychiatry, the term neologism is used to describe the use of words that only have meaning to the person who uses them, independent of their common meaning. This is considered normal in children, but a symptom of thought disorder (indicative of a psychotic mental illness, such as schizophrenia) in adults.
People with autism also may create neologisms.
Use of neologisms may also be related to aphasia acquired after brain damage resulting from a stroke or head injury especially to the Wernicke's Area which is mainly responsible for comprehension also known as Jagron aphasia.
In theology, a neologism is a relatively new doctrine (for example, rationalism). In this sense, a neologist is one who proposes either a new doctrine or a new interpretation of source material such as religious texts.