Om Soham is a Hindu mantra that literally means “I am That” in Sanskrit. The philosophical meaning is that the chanter is identifying oneness with the universe, the ultimate reality. The iconography associated with the mantra is a swan. Soham inverted is Hamsoh, which means swan. Here, the swan represents the Atman, or inner self, soul, true self beyond identification.
When you chant Om Soham, you are really saying: I am the universe, the cosmic swan, the phenomena that is the essence of the individual.