Calpurnia is a Roman family name — Calpurnia Pisonis (c. 75-14 BCE) was the third wife of Julius Caesar, who famously dreamed of his assassination the night before the Ides of March.
Calpurnia is rare but distinctive. Atticus Finch's housekeeper in To Kill a Mockingbird is named Calpurnia.
Calpurnia 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 Calpurnia reduce to 5, The Seeker. This is a traditional interpretive system, not a factual claim about the name.