paranoia (n.)

"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]

The morbid condition seems to have been noticed before. Middle English medical writing has suspecioushed "suspicioushood") for "pathological or delusional state of suspiciousness" (early 15c.).