"personal qualities, gifts of ability, share of mental endowments or acquirements," 1560s, from part (n.).
also scatter-brain, "thoughtless, giddy person; one incapable of serious, connected thought," 1790, from adjective scatter-brained (1764); see scatter (v.) + brain (n.). Scattered in the figurative mental sense is by 1620s, and the use of scattering for "mental distraction" dates to mid-15c. For the formation, compare scatter-good "spendthrift" (early 13c. as a surname).
mid-15c., distraccioun, "the drawing away of the mind from one point or course to another or others," from Latin distractionem (nominative distractio) "a pulling apart, separating," noun of action from past-participle stem of distrahere "draw in different directions" (see distract).
Sense of "a drawing of the mind in different directions, mental confusion or bewilderment" is from 1590s. Meaning "violent mental disturbance, excitement simulating madness" (in driven to distraction, etc.) is from c. 1600. Meaning "a thing or fact that causes mental diversion or bewilderment" is from 1610s.
"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]