What is "menapii"

The Menapii were a Belgic tribe of northern Gaul in pre-Roman and Roman times. According to descriptions in such authors as Strabo, Caesar, Pliny the Elder and Ptolemy their territory had stretched northwards to the mouth of the Rhine in the north, but more lastingly it stretched along the west of the Schelde river. In later geographical terms this territory corresponds roughly to the modern coast of Flanders, the Belgian provinces of East and West Vlaanderen. It also extended into neighbouring France and the river deltas of the southern Netherlands.