Three children born of a mother one right after another. A very derogatory term, the slur was actually a triple-whammy, implying that the Irish were more likely to bear children in quick succession because of the Catholic Church's proscription of birth control, less likely to restrain themselves from procreating, and unable to understand the proper meaning of the terms "twins" and "triplets."
While I can never call myself a triplet mom, I had three kids in a row and refer to them as Irish Triplets.
Three children, born in very quick succession. Often two of them are the exact same age for a short period of time. Derogatorily named for Irish Catholics who historically bred without regard to timing and birth control, but it happens to anyone.
"There goes that Canadian chick with her Irish triplets."