From The Influence of Byron on Emily Brontë, by Helen Brown in The Modern Language Review, Vol. 34, No. 3 (Jul., 1939), pp. 374-381:

...Unfortunately, we have practically no information as to what Emily read.... The only other clue is the song with which Nelly Dean sings the baby Hareton to sleep:

It was far in the night, and the bairnies grat,
The mither beneath the mools heard that—

These are two lines from a translation of an ancient Danish ballad, which was printed by Scott in the appendix to The Lady of the Lake....