* Imitate singing: Like a "la la la" but with a slightly more emphatic sound.
* Express happiness or silliness: It's a lighthearted way to convey joy or playfulness.
* Fill in a gap in a sentence: Sometimes it's used as a placeholder when someone can't remember a specific word or phrase.
It's similar to other nonsensical sounds like "ho ho ho", "boo boo", or "blah blah blah". They don't have a strict meaning but convey emotion or intention.