The name Garala Kantha is given to Lord Shiva mainly in Andhra Pradesh, Telangana and Karnataka. The word Garala means poison. Shiva who swallowed the dreadful poison Kalakuta, that came out of the churning of the ocean, to save the universe is called Garala Kantha.
Symbolically, the attractions of the world are poison. The senses are always attracted to worldly things that have no real value and meaning. The poison creates confusion in the minds of a devotee.
Worship of Shiva helps in not suffering due to the worldly poison.
The Devas and Asuras were churning the ocean to achieve immortality. They did not realize that immortality can only be achieved by merging with the Supreme Truth.
Human beings in Kali Yuga are constantly churned by materialistic desires. This never ending churning generates numerous kinds of poison. Shiva as Garala Kantha drinks all the poison to save the universe.