What were the people of the British Isles called back when it was called Albion?

Called by whom? Most country boundaries didn't exist. People were known by the tribal names.

There was no one name that covered everybody. The name Albion is Celtic in origin, but seems to have been a geographical term rather than one that described a people. Various peoples described themselves as Belgae or Brigantes or Picts - and each of these groups were subdivided into tribes or clans. The term Briton was also used - the Welsh described themselves as Britons as late as the early mediaeval period.

Barbarians

Perfidious.

Called by who? And in that period prior to the 6th century there were many different groups in the British Isle including but not limited to Picts, Scots, Welsh, Angles, Jutes ans Saxons.

Albumen

"Albion" was a name invented by people who did not live in the British isles. It refers possibly to the white cliffs of Dover ("Album" in Latin means "white"), as seen 20 miles away from the coast of France.

Celts and Ancient Britons inhabited the British Isles before the Roman invasion in AD 43. The Romans called it "Britannia", possibly after a local tribe in the British Isles. Since then, the population has been mixed, with further invasions by Saxons, and Angles, and Jutes, and Vikings, and Normans, etc.

Napoleon, just over 200 years ago, used the expression "Perfidious Albion".

it never been "called" Albion - but it has been referred to as Albion


just as you might refer to somebody as an "a//shole"

Sorry don’t know maybe google can help