"mental disorder characterized by systematized delusions of more or less definite scope," 1848 (earlier paranoea 1811), from Greek paranoia "mental derangement, madness," from paranoos "mentally ill, insane," from para- "beside, beyond" (see para- (1)) + noos "mind," which is of uncertain origin.
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]
c. 1600, "affected with mania, raving with madness," from French maniaque (14c.), from Late Latin maniacus, from Greek maniakos, from mania (see mania). Borrowed at first in French form. From 1727 as "pertaining to mania." The noun, "one who is affected with mania, a madman," is attested by 1763, from the adjective.