daffy (adj.)

"simple, wanting in intelligence," also "crazy, mad," 1884, perhaps from daft (adj.), or from obsolete daffe "a halfwit" (early 14c.; mid-13c. as a surname), which survived in 19c. in dialects, itself of uncertain origin (OED finds a proposed origin in Scandinavian words for "deaf, stupid," such as Old Norse daufr, "phonetically inadmissible"). Compare late 15c. daffish "dull-witted, spiritless." With -y (2). Related: Daffily; daffiness. The Warner Bros. cartoon character Daffy Duck debuted in 1937.