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).
Old Saxony
Old Saxony is the place from which most of the raids and later colonisations of Britain were mounted. The region was called "Old Saxony" by the later descendants of Anglo-Saxon migrants to Britain, and their new colonies in Wessex and elsewhere were the "New Saxony" or "Seaxna". In Germany the Saxon lands were known simply as "Saxony" (Modern German:"Sachsen") and only later came to be called "Lower Saxony", to differentiate those original Saxon tribal territories from what became the Kingdom of Saxony or "Upper Saxony" in territories far to the south-east of the original Saxon homeland. The Anglo-Saxon writer Bede claimed in his work "Historia ecclesiastica gentis Anglorum" (731) that Old Saxony was the area between the Elbe, the Weser and the Eider in the north and north west of modern Germany and was a territory beyond the borders of the Roman Empire.