- Cursus honorum
- The sequential ladder of public offices in ancient Rome — a structured political career path from minor magistracies up to consul or beyond, roughly equivalent to climbing the civil service.
- Praetorian Guard
- The elite personal bodyguard of the Roman Emperor, and the only military force permitted to carry weapons inside the city of Rome — giving them enormous political leverage over imperial succession.
- Julio-Claudian dynasty
- The first Roman imperial dynasty, spanning Augustus to Nero, comprising emperors who claimed lineage from either Julius Caesar (Julian) or the Claudian family — the bloodline that gives Claudius his place in power.
- Consul
- One of the two highest annually elected magistrates in Roman governance, originally the highest office in the Republic; under the Empire, the role retained prestige but was largely ceremonial.
- Cerebral palsy
- A group of permanent movement disorders caused by abnormal brain development or damage occurring before or during birth; modern historians have retroactively suggested Claudius may have suffered from it based on his recorded symptoms.
- Tourette's syndrome
- A neurological condition characterised by repetitive involuntary movements and vocalisations (tics), including involuntary utterance of words or sounds; proposed by the hosts as a possible explanation for Claudius's inappropriate outbursts.
- Phrenology
- The now-debunked 19th-century pseudoscience of reading character and intelligence from the shape of the skull; used here as a metaphor for judging worth by physical appearance.
- Betrothal
- A formal engagement or promise of marriage; in Roman society this could be arranged in childhood and carried legal and political weight, distinct from the actual marriage ceremony.
- Rhinorrhea
- Medical term for a persistently runny nose; cited in the episode as one of Claudius's chronic symptoms.
- Lugdunum
- The Latin name for the Roman city in Gaul that is now Lyon, France; the birthplace of Claudius and, as the hosts note, what makes him the first emperor born outside Italy.
- Betwixt
- An archaic or literary preposition meaning 'between'; Horatio Gould uses it deliberately for comic effect when placing Claudius 'betwixt the mad cunts' — i.e., between Caligula and Nero.
- Horseshoe theory
- The political idea that the far left and far right eventually circle back to resemble each other; used here metaphorically to describe how modern disability attitudes have looped back to resemble ancient ones, just inverted.
- Antonia the Younger
- Claudius's mother; daughter of Octavia Minor (Augustus's sister) and Mark Antony, making her blue-blooded Roman royalty — and the woman who called her son 'an abortion of a man.'
- Cursus honorum
- The sequential ladder of public offices in ancient Rome — a structured political career path from minor magistracies up to consul or beyond, roughly equivalent to climbing the civil service.
- Perfunctory
- Carried out with minimal effort or care, as a matter of routine; not used explicitly but implied by how Tiberius dismissed Claudius's three requests for political office.
- Sejanus
- The powerful Praetorian Prefect who effectively ran the Roman Empire while Tiberius was secluded on Capri; his eventual fall from power had direct knock-on effects for Claudius's marriages.
- AH (Anno Hegirae)
- The Islamic calendar year designation, meaning 'in the year of the Hijra' — Muhammad's migration from Mecca to Medina; the hosts note that the current Islamic year is 1447 AH, roughly 600 years behind the Gregorian calendar.
- Valeria Messalina
- Claudius's third wife, married when she was approximately 18 and he was nearly 50; she would become one of the most notorious women in Roman history, teased by the hosts as the subject of Part Two.