Another interesting case are ethnic Russians where 20 recurring men and women name (few pre-christian, and some christian) cover the bulk of a population of over 100m. I never found a satisfactory explanation why. What's more interesting is, my client was hiring branches of 20 employees, where you usually end up with 3 Olgas etc in one team, and people don't appear to be confused of who is meant when they say Olga.
My family is all Irish, and the family tree for my female relatives is a tour of every possible derivative of Mary. One group of sisters were named Mary, Molly, Margaret, Maura and Mary Kathleen.
