Here's what we know:
* It refers to a large, flat, circular basket: Usually made from woven bamboo or rattan, used traditionally for carrying and serving food, particularly during special occasions.
* It might be related to the word "bilog": Meaning "round" or "circular", which describes the shape of the bilao.
* It's likely a pre-colonial word: Meaning it existed before Spanish colonization of the Philippines, as there is no known Spanish influence in the word's etymology.
In conclusion: While the exact origin of "bilao" is unclear, it is a word deeply rooted in Philippine culture and represents a traditional and versatile household item.