The One who is Perfection.
The One who is Absolute Completion.
The One who is the Definition of Complete State of Shiva.
When Adya Kali stands with her right foot on the Manipura chakra of MahaKala Bhairava, he attains Shunyata and she attains PURNATA. She becomes the most Purna Form of MahaKala Bhairava.
Hence the name, PURNA