Language: Gurmukhi, Sanskrit
Source: Siri Guru Granth Sahib
This mantra has been given by Yogi Bhajan to be chanted to help release a soul when a person dies. It means that there is no death, only liberation. We are deathless.
All Sikh Guru's used this word. It is in the first daily prayer of the Sikh's, Japji Sahib, but has roots in Hindu, yogic traditions which go back further, therefore it is both Sanskrit and Gurmukhi in origin.
This mantra information is from Spirit Voyage