Just like "A Bunch of Thyme" that a type such as myself should sing the part of a broken hearted young girl with an unborn child is incongruous to say the least. It seems to work however.
This song is to be found in both in Soodlum's 100 Irish Ballads Volume 1
as well as in the Clancy Brothers' The Irish Songbook
but is probably has its origins in England.