Simplify the following text for a Grade 8 native English-speaking person.
Original: He is best known by his West Frisian nickname `` Grutte Pier '' ( `` Big Pier '' in the Old Frisian spelling ) , or by the Dutch translations `` Grote Pier '' and `` Lange Pier '' , or , in Latin , `` Pierius Magnus '' , which referred to his legendary size and strength .
Simplified: Donia was also known as Grutte Pier , which means `` Big Lad '' , in Frisian language , or Grote Pier , which means the same in Dutch language .