In Greek comedy, Eiron was a stock character. He was a dissembler, who characteristically spoke in understatement and deliberately pretended to be less intelligent that he was. He was the clever although deceitful character, who always triumphed over Alazon (who was the self-deceiving and stupid braggart-bully).
More generally, an eiron is anyone who hides under a false appearance or conceals the truth.
Eiron (eirön) is also sometime said to be the root for the English word irony. At the very least, it is closely related to whatever was the Greek root.