fa-la
Sung nonsense syllables
Fa-la is a refrain of nonsense syllables in Renaissance madrigals and similar songs, often repeated in patterns like "fa-la-la-la-la." The syllables filled musical phrases without adding textual meaning, creating a light, festive effect.
The convention survives in Christmas carols: Deck the halls with boughs of holly, fa-la-la-la-la.