Original: The oldest known document in Maltese is "Il Cantilena" (Maltese:Xidew il-Qada) a poem from the 15th century, written by Pietro Caxaro  and the first known Maltese dictionary was written by the French Knight Francois de Vion Thezan Court in 1640.
Simplified: The oldest known document in Maltese is "Il Cantilena," a poem from the 15th century written by Pietro Caxaro.