Middle English word meaning "conscience" (early 13c.), "reason, intellect" (c.1300), from in (adv.) + wit (n.). Not related to Old English inwit, which meant "deceit." Joyce's use in "Ulysses" (1922), which echoes the 14c. work "Ayenbite of Inwyt," is perhaps the best-known example of the modern use of the word as a conscious archaism.
Þese ben also þy fyve inwyttys: Wyl, Resoun, Mynd, Ymaginacioun, and Thoght [Wyclif, c.1380]
If ... such good old English words as inwit and wanhope should be rehabilitated (and they have been pushing up their heads for thirty years), we should gain a great deal. [Robert Bridges, 1922]
“Foreword” and “inwit” were good once; but “preface” and “conscience” 245 mean as much and have the advantage of being alive.
Death, however ignominious, rather than remorse—the backbite of inwit, in the quaint language of our forefathers.