
Britain was derived from the word "Britons," which is a
Celtic tribe that inhibited the island more than 2000 years ago. Phoenician traders were the ones who gave the tribe it's name.
After the
Gallic Wars, the southern part the island became a part of the
Roman Empire. As the Roman Empire weakened, the area was abandoned. Without the support of the Empire, the Britons could not help but succumb to the Germanic tribes' invasion. One of the Germanic tribes were called the Angles, which incidentally is where the name "England" came from.