Who is Kivke from Tevye the Dairyman and the Railroad Stories and what is their importance?

Kivke is a Jew who is arrogant and is sentenced to run the gauntlet of flogging. He avoids this when Reb Nissl arranges for Kivke to be declared dead and smuggled to Austria. In Austria, Kivke sends letters to Reb Nissl and blackmails him every year or so for more money.