Tellervo is the Finnish forest goddess from the Kalevala — daughter of Tapio (god of the forest) and Mielikki (forest queen). Protector of forest creatures and the moss.
Tellervo is widely used in Finland.
Tellervo 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 Tellervo reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.