The term is used to describe two children born to the same mother in the same calendar year or within twelve months of each other. The phrase originated as a derogatory term associated with Irish immigration to the United States and England in the 1800's. The implication was that large groups of close-in-age siblings were the result of uneducated, poor Irish Catholic families' lack of birth control as well as self-control.
In modern use, the term is not intended as an insult, but rather a description of siblings born close together. Irish twins are not actually twins and they are not the same as having twins, which are defined as two siblings born from the same gestation.
Also Known As: Irish triplets when three children are born to the same mother within three years.
A mother gives birth to one baby in January of 2007 and another child in December of the same year. Or, alternatively, a mother births a child in August of 2007, becomes pregnant again in October, and gives birth to another child in July of 2008.