We have two types of births. Birth from womb of the mother - physical birth. Birth from the womb of Sadguru - enlightened Master - Psychological birth. Birth from mother leads us to physical identity seeking happiness from the world. Birth from the womb of wisdom of Sadguru leads us to Seeking Happiness from the eternal Self within. This is like a metamorphosis.
Crawling caterpillar starts flying as colourful butterfly. Such a person who is born in Wisdom is called Dwija - Twice born.