Complex sentence: Both dialects are in fact "Austronesian" in both grammar and vocabulary, due to their original derivation from Motu; the dialect names refer to the "first languages" spoken by users of this lingua franca.
Split into simpler sentences: Both dialects are Austronesian in both grammar and vocabulary, due to their original derivation from Motu. The dialect names refer to the "first languages" spoken by users of this lingua franca.