Notable bearers of this name include the Greek philosopher and mathematician Theon of Smyrna (2nd century AD) and the Greek scholar and mathematician Theon of Alexandria (4th century AD).
In modern literature, this name is best known for being the name of Theon Greyjoy, a character from the A Song of Ice and Fire series of fantasy novels written by the American author George R. R. Martin (b. 1948). He also appears in Game of Thrones (2011-2019), a television series based upon the novels.
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).
This name has never been common in the English-speaking world, though it has been well-used elsewhere in Europe. A famous bearer was the Italian Renaissance master Raffaello Sanzio (1483-1520), usually known simply as Raphael in English.
However, it is possible that his aunt was either not telling him the (whole) truth or that Simpson had misremembered her words, as I have been unable to find a 1940s-era French or Italian actor whose given name or surname even remotely resembles Orenthal. In addition to this, research on FamilySearch learned that Orenthal was used as a given name in the United States long before Simpson: I came across men named Orenthal that were born in 1903, 1915, 1921 and so on.
Further research showed that a German surname of Orenthal once existed, as well as the rare Norwegian and Swedish surnames of Orendahl and Orendal. All of these surnames are probably locational surnames, since -dahl and -dal in Norwegian and Swedish surnames is usually derived from Norwegian and Swedish dal meaning "dale, valley", whereas -thal (and -tal) in German surnames is usually derived from Old High German tal meaning "valley".
If that is indeed true here, then the Norwegian and Swedish surnames are each probably a variant form of the surnames Arendahl and Arendal respectively, both of which refer to a place with that name (such as the city of Arendal in Norway or the suburb of Arendal in the Swedish city of Göteborg). The name of both of those places means "valley of eagles" and is ultimately derived from Old Norse ǫrn "eagle" and Old Norse dalr "dale, valley".
As for the German surname of Orenthal: I have been unable to find out from which place name the surname could have been derived. Perhaps we should take into account the possibility that it might be a patronymic surname instead, in which case it might possibly be derived from (or etymologically related to) the medieval German given name Orendel.
With that said: another surname that might be of note in regard to the given name Orenthal, is the Gaelic surname of Aurendal or Aurendel. It is likely a Gaelic (variant) form of Arundel, an English surname that is ultimately derived from either Norman French arondel meaning "little swallow" (as in, the bird) or from Old English harhune dell meaning "valley of the horehound flower".
To go back to O. J. Simpson's case again for a moment: if his aunt did indeed name him after an actor (or someone with an other profession in the entertainment industry), then this actor might not necessarily have been French or Italian (contrary to what she had later claimed), nor would his given name or surname necessarily have been Orenthal exactly. For example, it could be that she named Simpson after someone with the surname of Rosenthal, but swapped the places of the first two letters and dropped the 's'. If that is indeed true, then a 1940s actor that could have been a possible inspiration to her might have been Harry Rosenthal (c. 1893-1953), who was also a composer.
So, all in all, at this point in time it seems likely that the given name Orenthal ultimately goes back to a surname, but we might perhaps never know which one exactly.
In England Oliver was a common medieval name, however it became rare after the 17th century because of the military commander Oliver Cromwell, who ruled the country following the civil war. The name was revived in the 19th century, perhaps due in part to the title character in Charles Dickens' novel Oliver Twist (1838), about a poor orphan living on the streets of London. It became very popular at the beginning of the 21st century, reaching the top rank for boys in England and Wales in 2009 and entering the top ten in the United States in 2017.
Possibly taken from the plant family, Nerium oleander (flowering shrub known as oleanders), Cascabela thevetia (yellow oleander), Acacia neriifolia (oleander wattle); or a species of moth, Daphnis nerii (oleander hawk-moth).
In the complex language of love practiced during the time of Queen Victoria, the Oleander flower means caution.
A diminutive use of Oleander could be Ollie, Lee, Lee-Ann, or Anders.
This name is also common for girls in Estonia, though a connection to the English-language name is uncertain.
Apart from royalty, this name was only moderately popular in France during the Middle Ages. After the French Revolution, when Louis XVI was guillotined, it became less common.
The Normans brought the name to England, where it was usually spelled Lewis, though the spelling Louis has been more common in America. Famous bearers include French scientist Louis Pasteur (1822-1895), French actor Louis de Funès (1914-1983), Scottish author Robert Louis Stevenson (1850-1894), who wrote Treasure Island and Dr Jekyll and Mr Hyde, and American jazz musician Louis Armstrong (1901-1971).
Though it has never been popular in the English-speaking world among Christians, it has historically been a common name for Jews, who have used it as an Americanized form of names such as Isaac, Israel and Isaiah.
Saint Gervasius was an early martyr from Milan whose remains (along with those of Protasius) were discovered in the 4th century by Saint Ambrose. He was thought to have lived a century or two earlier.
This name has been used occasionally in England since the 12th century. It was not common in the English-speaking world until the end of the 20th century.
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.
This name was not particularly common in Western Europe during the Middle Ages. It became more popular in part due to the fame of Prince Eugene of Savoy (1663-1736), a French-born general who served the Austrian Empire. A notable bearer was the American playwright Eugene O'Neill (1888-1953).
In medieval Dutch literature, this is the name of the eponymous character of Karel ende Elegast ("Charles and Elegast"), a 13th-century epic poem about Charlemagne and his friend, the noble knight Elegast.
Famous bearers of the name include the English poet Edmund Spenser (1552-1599), the German-Czech philosopher Edmund Husserl (1859-1938) and New Zealand mountaineer Edmund Hillary (1919-2008), the first person to climb Mount Everest.
It has never been very common as a given name in the English-speaking world, though it rose in popularity after the middle of the 20th century. In the United States it is frequently an African-American name. In Lithuania it may be given in honour of the Lithuanian-American aviator Steponas Darius (1896-1933), who died attempting to fly nonstop from New York to Lithuania. His surname was an Americanized form of the original Darašius.
This name was borne by a number of important saints, including Cyril of Jerusalem, a 4th-century bishop and Doctor of the Church, and Cyril of Alexandria, a 5th-century theologian. Another Saint Cyril was a 9th-century Greek missionary to the Slavs, who is credited with creating the Glagolitic alphabet with his brother Methodius in order to translate the Bible into Slavic. The Cyrillic alphabet, named after him, is descended from Glagolitic.
This name has been especially well-used in Eastern Europe and other places where Orthodox Christianity is prevalent. It came into general use in England in the 19th 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 two 20th-century kings of Belgium. Other famous bearers include the German physicist Albert Einstein (1879-1955), creator of the theory of relativity, and Albert Camus (1913-1960), a French-Algerian writer and philosopher.
Alberich is a sorcerer dwarf who guards the treasure of the Nibelungen in the medieval German epic the Nibelungenlied. The dwarf also appears in Ortnit as a helper to the hero.