Shirley is from the Old English place-name scīr (bright) + lēah (clearing, meadow) — originally a Yorkshire surname. Popularized as a feminine first name by Charlotte Brontë's 1849 novel Shirley, where the heroine is named Shirley because her parents wanted a son. Author of Unbought and Unbossed (1970). Shirley Jackson (1916-1965) — The Lottery (1948).
Subject of Anastasia C.
Shirley 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 Shirley reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.