Getting caught up on some requests. Baby girl's name Rianne. Either from Welsh Rhiannon or from Irish Rían. Rhiannon is from the old Celtic name Rigantona meaning "great queen". In Welsh mythology Rhiannon was the goddess of fertility and the moon. Male name Rían (Ryan) means "king," or "little king." So either way, a feminine Rianne means "queen" or at least "royalty."