This was a common name in classical Greece, and, due to both the saints who carried it and the favourable meaning, it came into general use in the Christian world, being especially popular among Eastern Christians. It was however rare in Britain before the 19th century. Famous bearers include three tsars of Russia (in the Russian form Fyodor) and American president Theodore Roosevelt (1858-1919).
In some cases this name can be a short form of longer names that start with Leo, such as Leonard.
Though the etymology is unrelated, this is the name of a mountain on the island of Crete where, according to Greek myth, the god Zeus was born.
The Normans brought the name to England in the 11th century but it quickly died out. It was reintroduced by the German House of Hanover when they inherited the British throne in the 18th century. A famous bearer was Frederick Douglass (1818-1895), an American ex-slave who became a leading advocate of abolition.
Due to its favourable meaning, this name was popular among early Christians, being borne by many early saints and four popes. It has been used in England since the Middle Ages, though it has been more popular in continental Europe. A notable bearer was the German composer Felix Mendelssohn (1809-1847).
Due to the popularity of the saint, the name became common in the Christian world during the Middle Ages. The Normans brought it to England, where it was commonly spelled Cecily — the Latinate form Cecilia came into use in the 18th century.
As an English name it can also derive from the month of August, which was named for the Roman emperor Augustus.
This name was borne by the heroine of Lewis Carroll's novels Alice's Adventures in Wonderland (1865) and Through the Looking Glass (1871).
In Britain the parallel form Alice, derived via Old French, has historically been more common than Adelaide, though this form did gain some currency in the 19th century due to the popularity of the German-born wife of King William IV, for whom the city of Adelaide in Australia was named in 1836.