The given name Cailey originated as an English variant of the medieval Scottish name Cayley, which was derived from a Norman French surname meaning "from Cailloue-l'Éveque" (Bishop's Cailloue), a town in Normandy, France. The name's roots can be traced back to the 11th century during the Norman conquest of England.

The earliest recorded instance of the name Cailey dates back to the late 16th century when it appeared in parish records from Yorkshire, England. One of the earliest known bearers was Cailey Darlington, born in 1587 in Ripon, Yorkshire. Another early reference is found in the baptismal records of St. Mary's Church in Beverley, Yorkshire, where a Cailey Mauleverer was christened in 1602.

In the 17th century, Cailey Pierrepont (1607-1677) was an English politician who served as a member of parliament during the English Civil War. He supported the Parliamentarian cause and was a signatory to the death warrant of King Charles I in 1649.

During the 18th century, Cailey Willett (1725-1798) was a prominent English merchant and philanthropist from Southampton. He made significant contributions to the city's infrastructure and funded the construction of several bridges and public buildings.

In the 19th century, Cailey Coppinger (1822-1895) was an Irish-born explorer and naturalist who traveled extensively throughout South America and the West Indies. He made important contributions to the study of botany and zoology in the region.

Another notable bearer of the name was Cailey Morse (1853-1920), an American inventor and engineer from Massachusetts. He is credited with developing the first practical electric traction motor, which revolutionized the transportation industry and paved the way for electric-powered vehicles and trains.