Prior to 1922 Maplewood was part of South Orange. I think the area was first called Maplewood Station because that was what the railroad called the station. Pcg's research shows that even in the late 1800s the area had developed an identity separate from South Orange. This is probably why Maplewood is named Maplewood, not South Orange Township which is the case with Morris Township and Chatham Township.
The Village of South Orange separated from the rest of the Township of South Orange in 1903. In 1922 the Township of South Orange changed its official name to the Township of Maplewood. However, the name "Maplewood" had long been used to designate the locality.
Did it exist before 1922 as Maplewood?
From 1884 re 'James Ricolton" http://query.nytimes.com/mem/archive-free/pdf?res=9A0DEFD81038E033A25753C3A9679D94659FD7CF
From 1895 http://query.nytimes.com/mem/archive-free/pdf?res=9B04E2D81339E033A25751C1A9649C94649ED7CF
From 1889 http://query.nytimes.com/mem/archive-free/pdf?res=9C03E4DD123AE033A25752C2A9659C94689FD7CF