Caecilia is the Latin original of Cecilia — from caecus, meaning "blind." Saint Cecilia (2nd-3rd c.) was a Roman martyr who sang to God in her heart as she died. Patron saint of music and musicians.
Caecilia is the older Latin spelling — widely used in Germanic Catholic countries.
Caecilia 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 Caecilia reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.