Green’s Dictionary of Slang

(S.Afr.) a crazy person.

2003		IOL News Western Cape) 24 Oct. 🌐 Slang, patois, or dialect expressions such as [...] ‘mallit’.
2005		A. Lovejoy Acid Alex 194: The stupid bonehead bullies have never come across a mallit who knows how to fight in handcuffs. [Ibid.] 199: Real mallits just carried on normally in whatever derangement they were enjoying or enduring.