Y Ferch o'r Sker /The Maid of Sker.

This air comes from the Cambrian Minstrelsie, a 'National Collection of Welsh Songs' from 1893 collected and arranged by Joseph Parry and David Rowlands. The words set to it tell of the anguish of a jilted lover.
The name Sker itself is from the old Norse and means skerry ( or rocky islet).