Last name Caoin (Keen 
, Caoin) , globally, is a common family name. The family name Caoin is characteristic of New Zealand, where it is quite a common surname, Malaysia, and Guernsey (explore the name in all countries). Not in comparison with a country's population, it is commonest in the United States, Malaysia, and the United Kingdom. Very seldom, Caoin is the forename as well as the last name.