Sofonisba is from the Punic name Saphanba'al. Sofonisba Anguissola (1532-1625) was the first female painter of the Italian Renaissance to achieve major international reputation. Lived to be 93.
Sofonisba 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 Sofonisba reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.