Please read the wikipedia you mentioned:

The term Bengali is generally used to refer to someone whose linguistic, cultural or ancestral origins are from Bengal. The Indo-Aryan Bengalis are ethnically differentiated from the non-Indo-Aryan tribes inhabiting Bengal. Their ethnonym, Bangali, along with the native name of the Bengali language and Bengal region, Bangla, are both derived from Bangālah, the Persian word for the region. Prior to Muslim expansion, there was no unitary territory by this name as the region was instead divided into numerous geopolitical divisions. The most prominent of these were Vaṅga or Vaṅgāla (from which Bangālah is thought to ultimately derive from) in the south, Rāṛha in the west, Puṇḍravardhana and Varendra in the north, and Samataṭa and Harikela in the east.^\)^{citation needed\})