Janaki (जानकी) is an epithet of Sita — meaning "daughter of Janaka," the king of Mithila who adopted her. Sita is the heroine of the Ramayana, wife of Rama.
Janaki is widely used across India.
Janaki does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Janaki reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.