According to Wikepedia ..
Bayanihan is taken from the root word bayani meaning "hero". Thus, bayanihan means being a hero to one another. As in the classic tradition of carrying a house, each man carries a portion of the weight of the house and in effect, becomes a hero for all the others because he lightens the load for the others. Each man thus becomes a Hero to everyone as all the others become a Hero to him..
The origin of the term bayanihan can be traced from a common tradition in Philippine towns where community members volunteer to help a family move to a new place. The process involves literally carrying the house to its new location. This is done by putting bamboo poles forming a strong frame to lift the stilts from the ground and carrying the whole house with the men positioned at the ends of each pole. A mural by Filipino National Artist Carlos "Botong" Francisco illustrates the process. The tradition also features a small fiesta hosted by the family to express gratitude to the volunteers.