Hamsa is an Indian mantra, often repeated so’ham, “He am I” (while breathing in), hamsah, (while breathing out).
It expresses the unity of the devotee with God. When the first part alone is repeated rapidly, it sounds like hamso, the nominative of the name, hence the name. A.G.H.
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, p. 405