I first heard this Welsh lullaby in the film Empire Of The Sun (a brilliant film if you’ve not seen it before).
But the song itself is hauntingly beautiful.
Sleep my baby, at my breast,
’Tis a mother’s arms round you.
Make yourself a snug, warm nest.
Feel my love forever new.
Harm will not meet you in sleep,
Hurt will always pass you by.
Child beloved, always you’ll keep,
In sleep gentle, mother’s breast nigh
The story of the song can be found here, but first enjoy the performance.