This name was borne by the 4th-century saint Theosebia the Deaconess, who is venerated in the Eastern Orthodox Church.
In the case of the former, the first element is almost certainly derived from Greek φανός (phanos) meaning "light" (adjective) as well as "torch, lantern" (noun). The second element is possibly derived from Greek οὖρος (ouros) meaning "watcher, guardian", which might give the name the meaning of "guardian with a torch". Also compare Ourania and Orion, which might possibly be etymologically related to varying degrees.
In the case of the latter possibility, the name Phanourios might be a hellenization of the Arabic name Fannur (also written as Fanur), which is also strongly connected to the theme of light.
Due to the renown of the apostle, this name became common throughout the Christian world (in various spellings). In England the Normans introduced it in the Old French form Piers, which was gradually replaced by the spelling Peter starting in the 15th century [1].
Besides the apostle, other saints by this name include the 11th-century reformer Saint Peter Damian and the 13th-century preacher Saint Peter Martyr. It was also borne by rulers of Aragon, Portugal, and Russia, including the Russian tsar Peter the Great (1672-1725), who defeated Sweden in the Great Northern War. Famous fictional bearers include Peter Rabbit from Beatrix Potter's children's books, Peter Pan, the boy who refused to grow up in J. M. Barrie's 1904 play, and Peter Parker, the real name of the comic book superhero Spider-Man.
Due to the renown of the saints by this name, Gregory (in various spellings) has remained common in the Christian world through the Middle Ages and to the present day. It has been used in England since the 12th century. A famous bearer from the modern era was American actor Gregory Peck (1916-2003).
After the Norman Conquest this name became common in England. It was revived in the 18th century, perhaps in part due to Matthew Prior's 1709 poem Henry and Emma [2]. It was also used by Jane Austen for the central character, the matchmaker Emma Woodhouse, in her novel Emma (1816).
In the United States, it was third in rank in 1880 (behind only the ubiquitous Mary and Anna). It declined steadily over the next century, beginning another rise in the 1980s and eventually becoming the most popular name for girls in 2008. At this time it also experienced similar levels of popularity elsewhere, including the United Kingdom (where it began rising a decade earlier), Germany, France, Italy, Spain, Scandinavia and the Netherlands. Famous bearers include the actresses Emma Thompson (1959-), Emma Stone (1988-) and Emma Watson (1990-).