Guy de la Bedoyere

“The Greeks, at least by the fourth century BC, knew Britain as Albion. Originally applied to a Spanish tribe called the ‘Albiones’, the term was later adopted for Britain, perhaps because of its similarity to the Greek word for whiteness, alphos, thanks to the white chalk cliffs of the southeast coast. Pliny the Elder, writing in the first century AD, says that Britain had ‘previously’ been called Albion, so by then the name must have fallen out of common use.2 By the time Britain began to be referred to more frequently, the Greeks called it Prettannia, or Brettannia.3 What does seem certain is that in the fourth century BC, Pytheas of Massilia (Marseilles) sailed to Britain. Pytheas wrote down his experiences, but these only survive as incidental third-hand references by later writers. Most”
― Guy de la Bedoyere, Roman Britain: A New History