The name Casey has its origins in the Irish Gaelic language, deriving from the surname Ó Caisídhe, which means "descendent of the watchful one." It is believed to have emerged as a given name in the late 18th or early 19th century, primarily used in Ireland.

In ancient Irish mythology, the name is associated with the mythological figure Cásídhe, a renowned druid and seer known for his wisdom and prophetic abilities. This connection lends the name a sense of mysticism and foresight.

One of the earliest recorded instances of the name Casey can be found in the Irish Annals, which document the exploits of various noble families and individuals throughout Irish history. The name appears in reference to several historical figures, although exact dates are uncertain.

The first notable bearer of the name Casey was Cáisídhe Ó Maolchonaire (c. 1150-1220), a renowned Irish scholar and poet who was celebrated for his mastery of the Irish language and his contributions to the preservation of ancient Irish literature.

Another prominent figure was Tadhg Ó Caisídhe (c. 1450-1520), a Irish chieftain and warrior who played a significant role in the ongoing conflicts between Irish clans and the English forces during the Tudor conquest of Ireland.

In more recent history, Casey Stengel (1890-1975) was a legendary American baseball player and manager, best known for his tenure as the manager of the New York Yankees. He led the team to seven World Series championships and was inducted into the Baseball Hall of Fame in 1966.

Casey Jones (1863-1900) was an American railroad engineer who became a folk hero after sacrificing his life to prevent a train collision. His story was immortalized in the famous ballad "The Ballad of Casey Jones," which celebrated his bravery and dedication.

Casey Stoney (born 1982) is a former English professional footballer who played as a defender for several clubs, including Arsenal and Liverpool. She also represented the England national team and is currently the head coach of the Manchester United Women's team.

While the name Casey has gained popularity across various cultures and regions, its roots can be traced back to the rich heritage of Irish language and mythology, imbuing it with a sense of wisdom, foresight, and bravery.