"Danny Boy" is a ballad, written by English songwriter Frederic Weatherly in 1913, and set to the traditional Irish melody of "Londonderry Air".
The above text from the Wikipedia article "Danny Boy" text is available under CC BY-SA 3.0.

The "Londonderry Air" is an Irish air that originated in County Londonderry, Ireland. It is popular among the American Irish diaspora and is well known throughout the world. The tune is played as the victory sporting anthem of Northern Ireland at the Commonwealth Games. The song "Danny Boy" uses the tune, with a set of lyrics written in the early 20th century.
The above text from the Wikipedia article "Londonderry Air" text is available under CC BY-SA 3.0.