I’ve just finished reading an excellent book called Great Tales of English History, by Robert Lacey. In my view it should be made compulsory reading on the National Curriculum!
In it, he outlines one theory for the origin of the earliest known name for this island of ours. The first Celts who sailed to Britain from France are said to have named the new land after the white chalk cliffs, which would have been one of the most notable features as they approached across the narrowest stretch of sea between the two coastlines.
The word for “white” was Albion, which is still used at least in a poetic sense to this day.
(As so often happens in life, I came across this explanation twice within a few days!)