Balut could well be onomatopoeic for the involuntary sound somebody makes when first confronted with balut and forced to eat it. The most notorious Filipino snack, balut are chicken or most commonly duck eggs that are allowed to incubate for around two weeks, so that the egg has incubated right up to the point that a bird is almost formed, ready to hatch. That is often enough to put most people off, however when you get past the thought (and sight) of it, you have a nice cross in taste between duck meat and a boiled egg. Of course there is vinegar and salt on hand to season and take some of the edge off too.
A weird variation of the balut are the one day old, baby chicks that have only just hatched. They are male chicks that are not any use to the chicken farmers. They are deep fried and, like much of the Filipino street food, dipped into a big pot of vinegar, which is shared by everybody who eats there.