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).
Saxony
However, Sigismund, King of the Romans, had already granted Margrave Frederick IV the Warlike of Meissen (House of Wettin) an expectancy of the Saxon electorate in order to remunerate his military support. On 1 August 1425 Sigismund enfeoffed the Wettinian Frederick as Prince-Elector of Saxony, despite the protests of Eric V. Thus the Saxon territories remained permanently separated. The Electorate of Saxony was then merged with the much bigger Wettinian Margraviate of Meissen, however using the higher-ranking name Electorate of Saxony and even the Ascanian coat-of-arms for the entire monarchy. Thus Saxony came to include Dresden and Meissen. In the 18th and 19th centuries Saxe-Lauenburg was colloquially called the Duchy of Lauenburg, which in 1876 merged with Prussia as the Duchy of Lauenburg district.