Bihu (Assamese: বিহু, Hindi: बिहू) denotes a set of three different cultural festivals of Assam and celebrated by the Assamese diaspora around the world. Though they owe their origins to ancient rites and practices they have taken definite urban features and have become popular festivals in urban and commercialized milieus in the recent decades. One includes the Assamese new year celebrated in April. Bihu is also used to imply Bihu dance and Bihu folk songs. The Bihus are the national festivals of Assam. The most important festivals of Assam are the Bihus, celebrated with fun and abundance by all Assamese people irrespective of caste, creed, religion, faith and belief.
The word Bihu is derived from the language of the Dimasa people who have been agrarian since time immemorial. Their supreme god is Brai Shibrai or Father Shibrai. The First crops of the season are offered to Brai Shibrai while wishing for peace and prosperity. So Bi means "to ask" and Shu means "peace and prosperity" in the world. Hence the word BISHU gradually became Bihu to accommodate linguistic preferences.The other suggestion is that "Bi" means "to ask" and "Hu" means "to give" and so came BIHU. It was said by "Kalaguru" Bishnu Prasad Rabha. In Assam, Rongali Bihu draws from many different traditions— Austro-Asiatic, Sino-Burmese and Indo-Aryan—and is celebrated with great fervor. Celebrations begin in the middle of April and generally continue for a month. This is the traditional new year. In addition there are two other Bihus: Kongali Bihu in October (associated with the September equinox) and Bhogali Bihu in January (associated with the January solstice). Like most other Indian festivals, Bihu (all three) is associated with farming; as the traditional Assamese society is predominantly agricultural. In fact, similar festivals are also celebrated around the same time elsewhere in India.
Read more about Bihu: The Three Bihus, Rongali Bihu, Kongali Bihu, Bhogali Bihu, Instruments Used in Bihu, Bihu Elsewhere