Anglo-Frisian is a big word that means two groups of people who lived long ago in a place called Europe. The people in these groups spoke similar languages, which means the way they talked sounded alike.
The "Anglo" group lived in a place called England and the "Frisian" group lived in a place called the Netherlands and Germany. They were good at trading with each other, and sometimes they would visit each other's countries for fun.
Even though they lived in different places, the Anglo and Frisian people shared a lot of things in common. They both liked to farm and raise animals for food, and they enjoyed fishing from the nearby waters. They also enjoyed telling stories and singing songs to pass the time.
Over time, the languages that the Anglo and Frisian people spoke started to mix together. This meant that some words from each language sounded the same, and eventually, the two languages became more similar to each other. This mixing of languages is called language convergence.
Nowadays, the people in England still speak a language that comes from the Anglo group, which is called English. And the people in the Netherlands and Germany still speak a language that comes from the Frisian group, which is called Frisian. But if you listen closely, you can hear some similarities between the two languages, and that's because a long time ago, the Anglo and Frisian people were friends who liked to spend time with each other!