Crazy; nutty: You looney punk/ ''I think, sir, he's a little luny,'' replied Ginger Nut, with a grin (1853+)
noun(also loon or loonball): the inspired looney who hated killing/ would have shown up in a Mel Brooks epic had that loonball thought of it first (1884+)
[probably fr both lunatic and crazy as a loon (found by 1845)]