Cratylus (Κρατύλος) is the name of a dialogue by Plato, written in approximately 360 BC. In the dialogue, Socrates is asked by two men, Cratylus and Hermogenes, to tell them whether names are "conventional" or "natural", that is, whether language is a system of arbitrary signs or whether words have an intrinsic relation to the things they signify. In doing this, Cratylus became one of the earliest philosophical texts of the Classical Greek period to deal with matters of etymology and linguistics.
-- excerpted from wikipedia