Ireland - Passport & Nationality - Irish Citizenship by Descent (Indefinite Transmission)
If you were born outside Ireland to an Irish citizen (either a mother or father) who were themselves born outside of Ireland, then you will have a claim to Irish Nationality if their Irish Nationality was granted before your birth. This concept is known as "Indefinite Transmission", because Irish nationality could be passed down indefinitely (to children, grandchildren and grandchildren), irrespective of where they are born.
Watch this SHORT VIDEO by Philip Gamble on how Irish nationality is gained in this manner: