Some Tantric Masseuses prefer to be called Goddesses, and this is not out of their ego.It's a way of helping you to acknowledge that you are going to enter the feminine aspect of the Universe. From a Tantric point of view, the Universe consists of two fundamental opposites: Shiva and Shakti - masculine and feminine.
The Universe is a continuous dance between Shiva and Shakti. Matter (Shakti) appears out of the void (Shiva) and manifests into the physical world, only to be again reabsorbed into the infinite realm of Shiva.
Shakti has 10 aspects of her divine power, like 10 sides of the female aspect of the universe. They are often called Goddesses and they are worshipped through prayer and meditation.
When you go for a Tantric massage and the Goddess welcomes you into her world, you can emerge with her, and see the world from her eyes. Together you can maintain harmony and balance within the micro cosmos (you, the drop in the ocean) and the macro cosmos( the Universe, sometimes referred as the Ocean)