AUM

Without the use of the tongue, there are only three sounds you can utter: “aaa”,”ouuu”, and “mmm”.
Even if you cut off your tongue, you can still utter these three sounds. For any other sound, you need the use of the tongue. You are using the tongue only to mix the sounds. You know a mute person can only say “aaa”,”ouuu”, and “mmm”. He cannot say anything else because he had not learned how to use his tongue.

Now if you utter these three sounds together, What will you get? AUM.
AUM is not a religious trademark. AUM is fundamental sound in the existence.

-Sadguru