Simplify the following text for a Grade 8 native English-speaking person.
Original: Guelders or Gueldres ( Dutch : Gelre , German : Geldern ) is the name of a historical county , later duchy of the Holy Roman Empire , located in the Low Countries .
Simplified: Guelders or Gueldres ( Dutch : Gelre , German : Geldern ) is the name of a historical county . This became a duchy ( lands ruled by a duke or duchess ) of the Holy Roman Empire , located in the Low Countries .