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does anyone know the origins of "ohm"? why is it used to meditate?

well, "ohm" means "to praise" and
is a sound placed at the beginning
of a prayer to show an exclaimation.



for more information, i would suggest
going to wikipedia.com -[Haruko]

To my understanding it began as the Hindu "unstruck sound," the sacred vibration of the universe that is "unstruck" in being independent of causes (save perhaps the appearance of the universe itself). At least one source I've read (I believe by the modern yogi Iyengar...) parallels or equates Ohm with the 'cosmic background radiation' left over from the Big Bang. It was widely thought to "reside" in the heart or heart chakra and the "stilling" of the heart through yoga or meditation was thought to make the sacred sound detectable to the individual.

Buddhists seem to have widely adopted the Hindu convention of starting many mantras (in Sanskrit) with Ohm at the beginning, followed by a short to long series of words or syllables to produce a quasi-magical chant (which may or may not call upon the essence or energy of a particular spiritual being). Two famous Hindu mantras of this sort include OHM NAMAH SHIVAYA (roughly "O obeisance to Shiva") and OHM TAT SAT (a play on the verb "to be" that is sacred to Krishna-Vishnu according to the Bhagavad Gita). The most famous Buddhist chant of this sort is probably OHM MANI PADME HUM (roughly "O there IS a jewel in the lotus") associated with Avalokiteshvara/Chenrezig Bodhisattva, though I know a mantra sacred to Maitreya Bodhisattva of this formula (OHM MAITREYA MAIM).

Ohm may be pronounced as a single syllable though it is often subdivided into three separate parts for great effect, written in English as A-U-M. Physically it can be intoned in a 'trembling,' deep voice to really get the vocal cords and brain-pan vibrating. The vibration of the brain may aid in its effectiveness for religious practice (perhaps by increasing the rate of contact of neurotransmitters with nerve receptors?). Mentally one can contemplate the symbolic meanings attached to the sounds (e.g. the tripartite breakdown nicely fits with contemplation of Beginnings, Middles, and Ends) and one can concentrate on subtleties of the sounds (e.g. the dwindling exasperation that follows the MMMMMMMM of the long AUM incantation can be focused on to give a sense of "subtlety" that persists after the action is through, helping one perceive the Transcendent).