Katniss is the English common name of the edible aquatic plant Sagittaria — also called "arrowhead" or "duck-potato" — chosen by Suzanne Collins for her heroine to evoke wilderness, food gathering, and Diana the huntress. The name has been steadily entering US baby-name records since 2012, peaking at around 150 births per year. A modern feminist warrior archetype.
Katniss 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 Katniss reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.