A person's name sometimes tells us where their family first came from. 'Mac' or 'Mc' in a surname (for example, McDonald) is always either Scottish or Irish. "O" in a surname (for example, O'Brien) is always Irish. Other surnames, like Morgan and Jones, are Welsh.
Most British people speak English, but Gaelic is also spoken in the west and north of Scotland and in Northern Ireland. Welsh is spoken by over half a million people in Wales.