[Latin] nil nisi bonum [Notes] Short for nil nisi bonum de mortuis dicere. That is, "Don't speak ill of anyone who has died". Also "Nil magnum nisi bonum" (nothing is great unless good), motto of St Catherine's School, Toorak, Pennant Hills High School and Petit Seminaire Higher Secondary School. [Translation] 
(about the dead say) nothing unless (it is) good