Sonia is the Russian-Italian diminutive of Sophia — from the Greek sophia (wisdom). Grew up in a public housing project in the South Bronx; her father died when she was 9; her mother worked as a nurse to support her.
Sonia 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 Sonia reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.