Gopi is a word of Sanskrit (गोपी) originating from the word Gopala referring to a person in charge of a herd of cows. In Hinduism especially the name gopika (feminine form of Gopi) is used more commonly to refer to the group of cow herding girls famous within Vaishnava Theology for their unconditional devotion (Bhakti) to Krishna as described in the stories of Bhagavata Purana and other Puranic literatures. Of this group, one gopika known as Radha (or Radhika) holds a place of particularly high reverence and importance in a number of religious traditions, especially within Gaudiya Vaishnavism. In Gaudiya Vaishnavism, there are 108 gopikas of Vrindavan.
Bio from Wikipedia - See more on en.wikipedia.org Text under CC-BY-SA license