Green’s Dictionary of Slang

silly, foolish.

1945		Baker Aus. Lang. 130: Drongo and sonky, mean silly or foolish.
1952		West Australian (Perth) 23 Aug. 20/2: World War II gave us drongo (worthless).
1973		M. Harris Angry Eye 75: The Australian attitude of write-down-to-our-drongo readers leads to the endless flood of bad sporting books.
1996		(con. 1964-65) B. Thorpe Sex and Thugs and Rock ’n’ Roll 93: ‘He’s just the drongo bloody bass player’.