a serious mental illness marked by delusions of grandeur or persecution (that is, the person imagines himself to be a very important person whom many want to harm)
As paranoia took possession of his mind, he became convinced that the governments of the world wanted to kill him because he was the final avatar of Lord Vishnu.
para (beside, beyond)#noos (mind) (Greek)
In greek Para = out, Noia = Mind so mental disorder, Psychosis sounds like whine. Paranoia sounds like paranoid (people suffering from psychological disorder are considered as paranoid)