Rosie is the English diminutive of Rose — from the Latin rosa, the flower. The pet form has been used since the 19th century.
The British model Rosie Huntington-Whiteley is a contemporary bearer. Today Rosie sits in the U.S. top 500 and is rising fast.
Rosie 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 Rosie reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.