This was the name given to blacks in England and in America. It comes from the theory that the two underclass races would eventually merge together and form one race.
'No Blacks, No Irish, No Dogs' - sign posted on many places of work, phasing out a bit before the mid-20th Century. Many Irish pubs have an old sign like this put up above the door for ironic amusement and historical interest. As if to say, 'This is the way things were.'
"No -- We don't hire any paddies or smoked Irish here, now get to movin'"