Cosima is the Italian feminine of Cosmo — from the Greek kosmos, meaning "order" or "harmony of the universe." Cosima Wagner (1837-1930) was the daughter of Franz Liszt and wife of Richard Wagner.
Cosima is rising in modern British naming.
Cosima 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 Cosima reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.