Sometimes spelled as folderol, this nonsense word appeared in the 1800s in the refrain of songs. It's similar to tra-la-la but can also mean a useless ornament, bauble or trifle.
Here are some examples:
Robert Bell made note of the usage in a Yorkshire mummer's play in his book Ancient Poems, Ballads and Songs of the Peasantry Of England of 1857: “I hope you’ll prove kind with your money and beer, / We shall come no more near you until the next year. /Fal de ral, lal de lal, etc.”
noted these words of an old Yorkshire mummer’s play in his Ancient Poems, Ballads and Songs of the Peasantry Of England of 1857:
In Sketches By Boz, Charles Dickens wrote, “Smuggins, after a considerable quantity of coughing by way of symphony, and a most facetious sniff or two, which afford general delight, sings a comic song, with a fal-de-ral — tol-de-ral."