Gaelic. A lullaby for the baby Jesus. The singer (presumably Mary) describes the child's beauty, admits her role in great events, and praises the "white sun of hope"
It is not clear whether this is Scots or Irish Gaelic in origin. Kennedy-Fraser's version, from Eriskay with words from Allan Macdonald, is obviously Scots. The Digital Tradition version is said to be a translation by Seamus Ennis from Irish Gaelic.
The various translations have achieved some popularity in English based on the beautiful tune. - RBW