Upper Saxony
It was particularly to distinguish the lands from 'Lower Saxony', a concept which arose later in popular usage (though never enforced) as a term for the original Saxon lands in north and west Germany (where Low German dialects had spread), in what is now the state of Lower Saxony, as well as the adjacent Westphalian region, Holstein and the western part of today's Saxony-Anhalt north of the Harz range (Eastphalia).
Saxon Wars
The Saxons were divided into four subgroups in four regions. Nearest to the ancient Frankish kingdom of Austrasia was Westphalia, and farthest away was Eastphalia. In between these two kingdoms was that of Engria (or Engern) and north of these three, at the base of the Jutland peninsula, was Nordalbingia. Despite repeated setbacks, the Saxons resisted steadfastly, returning to raid Charlemagne's domains as soon as he turned his attention elsewhere. Their main leader, Widukind, was a resilient and resourceful opponent and accepted a peace offering from Charlemagne in a perilous situation, not losing face and preventing Charlemagne from continuing a bothersome war. This agreement saved the Saxons' leaders' exceptional rights in their homeland. Widukind was baptized in 785 and buried in the only Germanic church without a spire.