ιστάρχης
From LSJ
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
Greek Monolingual
ἱστάρχης, ὁ (Α)
ο ιστωνάρχης.
[ΕΤΥΜΟΛ. < ἱστός + -άρχης (< ἄρχω), πρβλ. γυμνασιάρχης, τελετάρχης].