How did the black Irish people come about?

I'm not too sure either. I have heard the myths about the Spanish though. There are a lot of people with the 'black irish' look too around Britain. Some variations on it some have jet black hair and blue/green eyes. Some with dark eyes, but most have really pale skin. The song 'Galway Girl' by Steve Earle mentions it 'her hair was black and her eyes were blue...'.