Kelsang is from the Tibetan སྐལ་བཟང་ (skal bzang — good fortune, good karma). Kelsang is one of the Tibetan unisex names — central to traditional Vajrayana Buddhist heritage.
Kelsang 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 Kelsang reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.