No, the ia, is used to form personal names and abstract nouns based on nouns and adjectives. It's a convention used to differentiate from saying "(The) rainbow (
Iris) is beautiful" from "(the person named)
Rainbow (Iridia) is beautiful". In English this is implied by context, capitalization and the presence of the Definitive or indefinite article, in Greek the suffix differentiates between a name and a simple noun.