Green’s Dictionary of Slang

(US) an eccentric, a mad person; hysteria.

[c.1367–86		Langland Piers Plowman (B) I Line 140: ‘Thow doted daffe’ quod she, ‘dulle are thi wittes’].
1901		Central Record (Lancaster, KY) 10 Oct. 4/4: Who said anything about the white house, you daffy.
1905		H. Green Actors’ Boarding House (1906) 127: Daffy in his day [...] had trained with the headliners in crookdom.
1919		C. Sandburg letter 17 Jan. in Mitgang (1968) 147: I wrote an article for you on the present hysteria of Europe, a touch of ‘the daffy,’ nearly everywhere.
1988		D. Woodrell Muscle for the Wing 128: The anarcho-capitalism of the street daffies was theorized, praised and practiced.
2001		S. King Dreamcatcher 562: He was like some daffy in-the-zone Vegas crapshooter rolling a string of sevens.