Trinovantum, in medieval British legend, is the name given to London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 in earliest times. According to Geoffrey of Monmouth

Geoffrey of Monmouth

Geoffrey of Monmouth was a cleric and one of the major figures in the development of British historiography and the popularity of tales of King Arthur...

's Historia Regum Britanniae

Historia Regum Britanniae

The Historia Regum Britanniae is a pseudohistorical account of British history, written c. 1136 by Geoffrey of Monmouth. It chronicles the lives of the kings of the Britons in a chronological narrative spanning a time of two thousand years, beginning with the Trojans founding the British nation...

(1136) it was founded by the exiled Trojan

Troy

Troy was a city, both factual and legendary, located in northwest Anatolia in what is now Turkey, southeast of the Dardanelles and beside Mount Ida...

 Brutus

Brutus of Troy

Brutus or Brute of Troy is a legendary descendant of the Trojan hero Æneas, known in mediæval British legend as the eponymous founder and first king of Britain...

, who called it Troia Nova ("New Troy"), which gradually corrupted to Trinovantum. It was later rebuilt by King Lud

Lud son of Heli

Lud , according to Geoffrey of Monmouth's legendary History of the Kings of Britain and related medieval texts, was a king of Britain in pre-Roman times. He was the eldest son of Geoffrey's King Heli, and succeeded his father to the throne. He was succeeded, in turn, by his brother Cassibelanus...

, who named it Caer Lud after himself, and this name became corrupted to Kaer Llundain, and finally London. This legend is part of the Matter of Britain

Matter of Britain

The Matter of Britain is a name given collectively to the body of literature and legendary material associated with Great Britain and its legendary kings, particularly King Arthur...

. In fact, the name London derives from Londinium

Londinium

The city of London was established by the Romans around AD 43. It served as a major imperial commercial centre until its abandonment during the 5th century.-Origins and language:...

, the name it was known by in Roman

Roman Britain

Roman Britain was the part of the island of Great Britain controlled by the Roman Empire from AD 43 until ca. AD 410.The Romans referred to the imperial province as Britannia, which eventually comprised all of the island of Great Britain south of the fluid frontier with Caledonia...

 times.

The name Trinovantum derives from the Iron age

Iron Age

The Iron Age is the archaeological period generally occurring after the Bronze Age, marked by the prevalent use of iron. The early period of the age is characterized by the widespread use of iron or steel. The adoption of such material coincided with other changes in society, including differing...

 tribe of the Trinovantes

Trinovantes

The Trinovantes or Trinobantes were one of the tribes of pre-Roman Britain. Their territory was on the north side of the Thames estuary in current Essex and Suffolk, and included lands now located in Greater London. They were bordered to the north by the Iceni, and to the west by the Catuvellauni...

, who lived in Essex

Essex

Essex is a ceremonial and non-metropolitan county in the East region of England, and one of the home counties. It is located to the northeast of Greater London. It borders with Cambridgeshire and Suffolk to the north, Hertfordshire to the west, Kent to the South and London to the south west...

, Suffolk

Suffolk

Suffolk is a non-metropolitan county of historic origin in East Anglia, England. It has borders with Norfolk to the north, Cambridgeshire to the west and Essex to the south. The North Sea lies to the east...

 and part of Greater London

Greater London

Greater London is the top-level administrative division of England covering London. It was created in 1965 and spans the City of London, including Middle Temple and Inner Temple, and the 32 London boroughs. This territory is coterminate with the London Government Office Region and the London...

, and who are mentioned by Julius Caesar

Julius Caesar

Gaius Julius Caesar was a Roman general and statesman and a distinguished writer of Latin prose. He played a critical role in the gradual transformation of the Roman Republic into the Roman Empire....

 in his account of his expeditions to Britain in 55 and 54 BC. In a later account of these expeditions by Orosius, they are referred to as civitas Trinovantum, "the tribe of the Trinovantes", with Trinovantum in this case being in the genitive

Genitive case

In grammar, genitive is the grammatical case that marks a noun as modifying another noun...

 plural

Plural

In linguistics, plurality or [a] plural is a concept of quantity representing a value of more-than-one. Typically applied to nouns, a plural word or marker is used to distinguish a value other than the default quantity of a noun, which is typically one...

. However, as civitas can also mean "city" and Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 neuter

Grammatical gender

Grammatical gender is defined linguistically as a system of classes of nouns which trigger specific types of inflections in associated words, such as adjectives, verbs and others. For a system of noun classes to be a gender system, every noun must belong to one of the classes and there should be...

 noun

Noun

In linguistics, a noun is a member of a large, open lexical category whose members can occur as the main word in the subject of a clause, the object of a verb, or the object of a preposition .Lexical categories are defined in terms of how their members combine with other kinds of...

s often end in -um in the nominative

Nominative case

The nominative case is one of the grammatical cases of a noun or other part of speech, which generally marks the subject of a verb or the predicate noun or predicate adjective, as opposed to its object or other verb arguments...

 singular

Grammatical number

In linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions ....

, this phrase has been misinterpreted by Geoffrey or his sources as "the city Trinovantum".