The ExoWorlds list of exoplanets and their host stars being available for public naming at the initiative of the IAU is a list compiled from several exoplanet databases, including exoplanet.eu  and exoplanets.org .
This list includes well-studied exoplanets discovered over twenty years, up to 31 December 2008. A period of at least five years since the discovery has been considered as a simple and satisfactory criterion to include exoplanets which can be considered as confirmed. All the discoveries were made using various methods, including radial velocities, transits, microlensing and direct imagery.
For these exoplanets, the scientific nomenclature follows the nomenclature rules widely adopted by the scientific community, which are drawn from the rules for naming binary stars. For each planet, the name of the host star (around which planets are orbiting) is followed by a lower-case letter: b for the first discovered exoplanet, c for the second, etc. (The letters are capitalized in the case of binaries: the "primary" star name is followed by "A", and its companion stars are labelled by the same name followed by "B", "C", etc.).
In the ExoWorlds list, five stars already have common names: Fomalhaut (alpha Piscis Austrini) is one of the four “royal stars” of ancient Persia, with Aldebaran, Antares, and Regulus; Pollux (beta Geminorum) is the twin brother of Castor, son of Zeus (Jupiter) and Leda, from the ancient Greek and Roman mythologies — the constellation Gemini is named after them (Gemini means twins in latin). Three other stars also have common names: gamma Cephei (Errai, Arabic for shepherd), epsilon Tauri (Ain, Arabic for the bull's eye) and iota Draconis (Edasich, Arabic also). These stars have common names as well in other cultures .
Consequently these five stars cannot be considered for public naming.
 Kunitzsch, P, and Smart, T., 2006, "A Dictionary of Modern Star Names" (2nd Revised Edition, Sky Publishing, Cambridge, MA, USA)
 Schneider, J., Dedieu, C., Le Sidaner, P., Savalle, R., and Zolotukhin, I. 2011, “Defining and cataloging exoplanets: the exoplanet.eu database”, Astronomy & Astrophysics, vol.532, id.A79, 11 pp.
 Wright, J. T., Fakhouri, O., Marcy, G. W., Han, E., Feng, Y., Johnson, John Asher, Howard, A. W., Fischer, D. A., Valenti, J. A., Anderson, J., Piskunov, N. 2011, “The Exoplanet Orbit Database”, Publications of the Astronomical Society of the Pacific, Vol.123, issue 902, pp.412-422.