Cassidy is a given name derived from an Irish

Irish language

Irish , also known as Irish Gaelic, is a Goidelic language of the Indo-European language family, originating in Ireland and historically spoken by the Irish people. Irish is now spoken as a first language by a minority of Irish people, as well as being a second language of a larger proportion of...

 surname and ultimately from the Gaelic given name Caiside, meaning "clever" or "curly-haired." The name Caiside comes from the Gaelic word element cas, according to "Behindthename.com"

Cassidy was the 244th most popular name for girls born in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 in 2009. It was most popular in 1999, when it was the 99th most popular name for American girls. It first appeared among the 1,000 most popular names for American girls in 1981. Kassidy, an alternate spelling, was ranked as the 443rd most popular name for girls in 2009. Cassidy last appeared among the top 1,000 names for American boys in 1992. It was among the top 1,000 names for American boys between 1983 and 1992; its highest ranking was 666th most popular name for boys born in 1984.

People with the name

• Cassidy (musician)
  Cassidy (musician)
  Cassidy now professionally known as akaCassidy and most recently Bohème was the lead singer for the band Antigone Rising from 1999 through 2008. Born January 15, 1979, in Tom's River, New Jersey to a young single mother who gave her up for adoption to the Catanzaro family from Garfield, NJ...
  
  , lead singer of Antigone Rising
• Cassidy (rapper), American rapper
• Cassidy O'Reilly
  Cassidy O'Reilly
  Cassidy Riley is an American professional wrestler, also known as Cassidy Reilly and Cassidy O'Riley best known for work with Total Nonstop Action Wrestling and World Wrestling Entertainment....
  
  , American wrestler

Fictional

• The Star Trek: Deep Space Nine character Kasidy Yates
• The fictional character Cassidy Chacon W.I.T.C.H.
• The fictional character Cassidy "Beaver" Casablancas on Veronica Mars
  Veronica Mars
  Veronica Mars is an American television series created by Rob Thomas. The series premiered on September 22, 2004, during television network UPN's final two years, and ended on May 22, 2007, after a season on UPN's successor, The CW Television Network. Veronica Mars was produced by Warner Bros...
  
  .