The Common Endings of Cities in the UK

Today, I memorized the 100 biggest cities in the UK and noticed that many of them share common endings. Some, like '-port,' '-field,' and '-pool,' are easy to understand, but others are hard for me to figure out. If you know the meanings or the geological/historical reasons behind the following endings, please let me know:

1. '-ham' (e.g., Birmingham, Nottingham, Cheltenham, Rotherham, Oldham, Gillingham)
2. '-ford' (e.g., Oxford, Watford, Telford, Chelmsford, Bedford)
3. '-mouth' (e.g., Portsmouth, Plymouth, Bournemouth)
4. '-hampton' (e.g., Northampton, Southampton, Wolverhampton)