Cassidy is from the Irish surname Ó Caiside — from casideach ("curly-haired" or "clever"). A top-100 US baby name from 1996 to 2002, peaking at #99 in 1999. Cassidy Hutchinson (born 1996) — American former White House aide; in June 2022, became one of the most consequential witnesses before the US House Select Committee on the January 6 Attack, delivering testimony about then-President Trump's behavior in the West Wing during the Capitol riot. *Her 2023 memoir Enough was a New York Times bestseller. Eva Cassidy (1963-1996) — American singer-guitarist whose recordings became internationally famous only after her death from melanoma at age 33; her version of "Over the Rainbow" topped the UK charts in 2001, five years posthumously. The story of her posthumous fame is one of the most-cited in 21st-century music history. David Cassidy is male (The Partridge Family*). Hopalong Cassidy is male (1935 character). Butch Cassidy is male (Sundance Kid partner).
Featured throughout 1990s American TV and 2020s political-history retrospectives.
Cassidy 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 Cassidy reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.