ἔγνω δὲ φώρ τε φῶρα καὶ λύκος λύκον → the thief knows the thief and the wolf knows the wolf, and thief knows thief and wolf his fellow wolf, set a thief to catch a thief
inter-mĕdĭus: a, um, adj.,
I that is between, intermediate (ante - class. and late Lat), Varr. R. R. 3, 5, 11; Paul. Nol. Carm. 26, 637.