Gurumukhi literally means “from the mouth of the Guru”. While we can explain the literal and philosophical meaning of the mantras in any language, the real potency of it lies with reciting it in the original Gurumukhi and experiencing the Naad, the energetic vibration of it. There are 84 meridian points in the mouth that are stimulated by the tongue while reciting mantra. This causes the glands to secrete and the brain to be positively affected. This stimulation boosts the functions of the neurological and endocrine systems and the effect in the vagus nerve reduces stress and promotes a sense of well-being.
When we repeat the words we qualify ourselves into the level of what that word mean, and align ourselves with the Naam, the energy vibration which is God.
This applies to a number of ancient, mystical languages like Arabic, Sanskrit, Latin etc.