Simplify the following text for a Grade 17 native English-speaking person.
Original: The origins of Valencian pilota are not known with certainty , but it is commonly supposed to have been derived from the medieval Jeu de paume along with several other European handball sports ( for example the Basque laxoa , French Longue paume , Frisian handball and Italian Pallone ) similar to the actual Valencian llargues variant .
Simplified: Valencian pilota origins are not known with certainty , but it 's commonly supposed to be a variant from the middle-aged Jeu de paume , as many other European handball sports ( Basque laxoa , French Longue paume , Frisian handball and Italian Pallone ) similar to the actual Valencian llargues variant .