REVERIE, a condition of mental abstraction, a fit of musing, a "brown study" ("brown" in the sense of "gloomy," and not to be referred to Germ. Braune, brow). The word appears in the 14th or 1sth centuries in its original meaning in Old French, of joy, delight, also wildness, anger. The French rever, later resver, modern river, to dream, meant originally to wander in speech or thought, and is derived from the Lat. rabiare, cf. " rabies," " rage " and " rave." The French reverie (resverie) was adopted again in the 17th and 18th centuries as meaning a state of dreaminess; thus Locke (Essay on the Human Understanding, 1695, ii. xix.) says: " When ideas float in our minds without any reflection or regard of the understanding, it is that which the French call resvery; our language has scarce a word for it."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)