There is a deep connection between cow and Lord Vishnu in
Hinduism. The belief is that cows represent Mother Earth and Lord Vishnu
resides in the cow and protects Mother Earth.
When there is rise in evil on earth, Mother Earth takes the
form of a cow and pleads to Lord Vishnu to protect Her.
Sri Krishna is also Govinda.
‘Govu’ means cow. It is clearly mentioned in Srimad
Bhagavata Purana that Sri Krishna who spends his childhood in Gokula amidst cows
is Govinda. Since he is the one who made gopalak (cowherd boys) happy, he is
called Govinda. Vishnu became famous in Dwapara Yuga with the name Govinda.
Srimad Bhagavata Purana elucidates the reason for Lord Krishna
gaining the name of Govinda. In Vrindavan, Nanda Maharaj wanted to perform
Indra Yag. But seven-year-old Krishna resisted it. He suggested that they
should perform Govardhan Puja instead. Enraged with this, Indra sent out
fierce rain with hailstones on the kingdom. Then Krishna, lifted the mountain (Govardhana)
and saved the residents of Brindavan and the cows. For this, a cow with the
name Surabhi showered milk on Krishna present to the delight of rishis,
devatas. Since Krishna protected cows and he became popular as Govinda, As
such, Sri Krishna continued to be worshipped as Govinda since Dwapar Yug. Even
in Kali Yug people chant his name and get ecstatic.
Krishna has stated in the Uddhava Gita and Bhagavad Gita
that I am Kamadhenu among the holy cows.