Simplify the following text for a Grade 11 native English-speaking person.
Original: The first widespread use of `` Palestinian '' as an endonym to refer to the nationalist concept of a Palestinian people by the local Arabic-speaking population of Palestine began prior to the outbreak of World War I , and the first demand for national independence was issued by the Syrian-Palestinian Congress on 21 September 1921 .
Simplified: The first demand for an Arab state encompassing Palestine was issued by the Syrian-Palestinian Congress on 21 September 1921 .