A simpleton. The word appears as Gonnie, a. 1580: N.E.D.
183740. That are Sheriff was a goney.Haliburton, The Clockmaker, p. 139. (N.E.D.)
1843. How the goney swallowed it all.Sam Slick in England, chap. xxi.
a. 1855. A stupid fellow, a dolt, a boot-jack, an ignoramus, is called here a gonus.Dartmouth Mag., iv. 116 (Halls College Words, p. 229).