Recorded in 《
水浒全传》 (Outlaws of the Marsh, Ming dynasty), chapter 7:
这伙人不三不四 - 'this bunch of people are neither one thing nor the other'. The numbers
三 and
四 historically symbolized propriety (heaven / earth / man, the four cardinal directions); 'not three not four' meant outside the proper order - hence shady or improper.
