Surname 시헌 (시헌 
, Sheahan 
, Siheon ) , in all the world, is quite a common cognomen. The family name 시헌 is characteristic of Ireland, where it is quite a common surname, Australia, where it is quite a rare surname, and New Zealand. Not in comparison with a country's population, it is the most numerous in the United States, Ireland, and Australia. Very seldom, 시헌 is the forename as well as the last name.