Cornwall is something of an oddity. The most south-westerly point of Great Britain, it was to this rocky promontory (and Wales) that the Celtic tribes were pushed by the invaders. As a result, the place names in Cornwall tend to be different from those in any other part of England. Many start with the letters "Tre" - Trevivian, Trelawney - or "Pol" - Polperro. There is a distinct similarity between Cornwall and Brittany, in France. Both were Celtic strongholds and as well as topographical similarities, there is the similarity of the ancient languages and the fact that Cornwall and Brittany have the world's only black and white flags.
But I'm digressing again.
Many English place names end in "chester" or similar - Chester itself, Rochester, Winchester, Chichester, Gloucester, Worcester, Leicester to name but a few. That is because these were Roman fortified sites and the names are based on the Old English, from the Latin castra, a camp.
"Ham" is a common ending in town names, as in Chatham, Nottingham, Tottenham, Oldham.
This comes from the Saxon for farm or homestead. In some instances the prefix refers to the situation of the homestead (the Chat of Chatham could refer to the valley in which the farm was situated) while others refer to the name of the homestead owner. The insertion of "ing" as in Gillingham means the family or people of the person named, so Gillingham means a homestead of Gylla's family, from Old English ham (village, homestead) and ingas (family, followers).
Then there are many "tons" - Crediton, Honiton, Northampton, Southampton. "Ton" meant a place surrounded by a hedge or palisade.
"Borough" - Edinburgh, Middlesbrough, Peterborough, Canterbury - comes from the Anglo-Saxon "beorgan", to shelter. An earthwork, and hence a fortified town.
And what of Brighton? Well, it was at one time Brighthelmstone and was abbreviated a couple of hundred years ago, There are various suggestions about the source and meaning of this name, such as these I have copied from www.mikeperris.com:
The origin of the name of Brighton is somewhat contentious. It has been translated as "a sea town with a bright or burning watchtower", or named in reference to the brightly decorated helms of the local ships, or "the divided town" (Brist meaning divided in ancient British, with the old river Wellesbourne doing the dividing), but the following seems to be the most common account:Oh well, you pays your money and makes your choice.
Within the small area of North, West, East and South Streets, the invading Saxons built a group of villages, one of which was called Bristelmestune, named after Brighthelm, who was either a Saxon priest (in France) or a Saxon warrior (killed on the South Downs), or possibly a Saxon farmer, depending on which account you read, although the warrior angle crops up more often than the others. According to a number of sources, including an article in the Daily Telegraph, Brighthelm is said to mean Bright Helmet, although I can only guess whether the words "bright" and "helmet" would have had any meaning to Saxons. Anyway, a shiny helmet appears prominently, if unofficially, in Brighton's coat of arms.