Yours, Etc.: Origins and Uses of 8 Sign-Offs
"mental disorder characterized by systematized delusions," 1848 (earlier paranoea 1811), from Greek paranoia "mental derangement, madness," from paranoos "mentally ill, insane," from para- "beside, beyond" (see para- (1)) + noos "mind."
FOR several years frequent descriptions have been given in the foreign journals, especially German and Italian, of the forms of insanity designated by the names Paranoia, Verrücktkeit, and Wahnsinn. ["Paranoia -- Systematized Delusions and Mental Degenerations," J. Séglas (transl. William Noyes), 1888]
paranoia par·a·noi·a (pār'ə-noi'ə)
A psychotic disorder characterized by systematized delusions, especially of persecution or grandeur, in the absence of other personality disorders.
Extreme, irrational distrust of others.
Note: In popular terminology, a “paranoid” personality is characterized by suspicion and distrust of others; a tendency to look for hidden meaning behind other people's actions; argumentativeness; complaining; low tolerance for criticism; and a constant display of one's own talents, accomplishments, independence, and rationality.