I don't remember where I was when I first heard that expression here, but I remember the explanation I got when I asked the man who used it what it meant. He told me that it was a reference to the fact that most men worked outside in the old days and those who worked the hardest got the darkest. The 'blacks' were those who worked the hardest of all.
I had no idea whether he was right or not. I was a twenty-year old student from New York and very tuned in to any racial overtones in language, which is why I asked. A few days later a woman described her son as 'black' from being out in the hot sun. The fact that the temperature was in the mid 70s and this guy was paler than any of my Italian friends in mid-January was irrelevant. He was no longer ghostly white and, therefore, 'black'.
'Black' is a relative term in a country where sunglasses are necessary at the sea-side so that the sun's reflection off the sun-bathers doesn't cause eye damage (and, yes, I fit in perfectly here on that score). And, although there are a fair number of black people in Ireland today, when I first came here there were, for all intents and purposes, none. I didn't see one black person during my three weeks here on vacation in 1985. Nor did Muhammad Ali, who famously asked where were all the "brothers" when he was here in 1972.
So, I was surprised by the minor ruckus caused by Mary O'Rourke's use of the phrase the other day. Some people would like Mary O'Rourke to apologize for her racial slur, which would be odd if the explanation I was given was correct. It would hardly make sense for O'Rourke to apologize to black people for using an old expression that really has nothing to do with black people.
Richard has followed this one closely and believes that O'Rourke has shown herself to be a racist in some of her interviews given subsequent to her remark. He may be right, but that doesn't necessarily mean the expression itself has anything to do with race. It may now be understood that way by a majority of the young, cosmopolitan, predominantly indoor-working Irish people, but that doesn't automatically mean the use of the phrase is a sign of anything other than the fact that the speaker may have grown up in a different Ireland. An Ireland where 'black' meant any shade darker than milk.