"Tralalero" and "Tralala" are nonsensical or playful terms often used in songs or casual speech to represent a carefree or happy sound, similar to "la la la" or "tra la la." They don't have a specific meaning but convey light-heartedness, joy, or a sense of whimsy.
They're commonly used in folk songs, children’s rhymes, or playful contexts to evoke a fun, carefree mood. For example, in some songs, you might hear these words used to fill space between verses or to add rhythm to a tune.