Bohag Bihu (also known as Rongali Bihu), which almost coincides with Poila Baisakh in Bengal, Baisakhi in Punjab, Vishu in Kerala and Puthandu in Chennai, is celebrated to observe the Assamese New Year. Mainly a harvest festival, there are three kinds of Bihu in Assam—Magh Bihu, Kati or Kongali Bihu and Bohag or Rongali Bihu.
The word Bihu is derived from the Sanskrit word Bishu which means “to ask blessings and prosperity from the Gods during harvesting season”. As the name suggests, Bihu, besides being a festival of joy and colours, also is the occasion during which farmers and people offer their prayers and gratitude to Gods for the prosperous harvest.
Every year Rongali Bihu is celebrated for seven days, which are known as Chot Bihu, Goru Bihu, Manuh Bihu, Kutum Bihu, Senehi Bihu, Chera Bihu and Mela Bihu. The first day of Bihu is called Goru Bihu during which cows are worshiped (g oru means a cow in Assamese). This day is of great significance for farmers, especially those who still depend on cows for tilling their land. On this day, they wake up quite early and take their cows to a nearby river bank or a pond. They bath (clean) the cows, worship and feed them. Here’s a special song that people sing while pampering and worshipping the cows:
Lao kha, bengena kha,
Bosore bosore barhi ja,
Source : https://timesofindia.indiatimes.com/life-style/events/bihu-2018-wishes-quotes-messages-sms-and-images/articleshow/63747506.cms