Image of Shakyamuni Buddha, the historical Buddha
name of Sakyamuni in Siddam
śā kya mu ṇi

Śākyamuni is a name for the nirmana-kāya aspect of the Buddha, and is therefore considered by Buddhists to be synonymous with the historical Buddha. In early texts the Buddha is most often referred to as Bhagavat or "the Blessed One", or as Gautama (Pāli Gotama) his clan name. He refers to himself as tathāgata or sugata. We refer to him as "the Buddha". Buddha is the past-participle of the verb budh ('to awaken') and thus means 'awakened'.

It is said that the historical Buddha grew up in a life of luxury but after seeing that everyone would grow old, become ill, and die, he abandoned his home and joined a group of ascetics seeking the way beyond death. Subsequently he abandoned severe asceticism as well and pursued a middle way between hedonism and asecticism that enabled him to make a decisive breakthrough known as bodhi, awakening, usually translated as enlightenment. He spent the rest of his life teaching others how they could also awaken.

Seed Syllables

Seed syllable 'a' in the Siddham script
'a' in
Siddham
 		 The letter a is the source of all the other letters, the source of all mantras.
a in Tibetan
(Uchen)
Seed syllable bhah in the Siddham script
bhaḥ
in Siddhaṃ		 In the Shingon school the seed-syllable of Śākyamuni is bhaḥ. This comes from the first letter of the most common way of addressing, or referring to, the Buddha - bhagavat - with the visarga (ḥ). The visarga is a common indicator of a bīja in early tantra, but is eclipsed by anusvāra (ṃ) in later traditions.

the word bhagavat in Siddhaṃ
bhagavat in Siddhaṃ

mantra

Siddhaṃ

Shakyamuni mantra in the Siddham script

Tibetan Uchen

Shakyamuni mantra in the Tibetan Uchen script

Devanāgarī

Shakyamuni mantra in the Devanagari script

Lantsa

Shakyamuni mantra in the Lantsa script
 

Transliteration

oṃ mu ni mu ni ma hā mu ni śā kya mu ni svā hā

oṃ muni muni mahāmuni śākyamuni svāhā

Alternate Tibetan Mantra

Shakyamuni mantra in the Tibetan Uchen script

oṃ muni muni mahāmuniye svāhā

Notes

Muni is an ancient Indian word for a sage, usually associated with silent sages. Śākya (Pāli Sakka) is the name of the tribe from which the historical Buddha came from, so Śākyamuni is the sage of the Śākyan tribe. Some scholars have tried to identify the Śākyans with the Scythians, known as the Śaka in Buddhist texts. This is extremely unlikely.

The alternate mantra uses the dative form of the word mahāmuni indicated by adding 'ye', which indicates the dative case meaning "to or for the great sage". You may also sometimes see the -ye suffix added to Śākyamuni in the standard version.

Professor Richard Gombrich pointed out in his Numata Lectures in 2006 that when -gata is used in compounds of this type it loses its primary meaning and means simply being. Tathāgata then would mean "one who is like that". See for instance Michael Coulson's Teach Yourself Sanskrit, p.111. "This is tantamount to saying that there are no words to describe his state; he can only point to it" (Gombrich 2006 : lecture 6, and forthcoming). However Buddhists most often take tathāgata to mean "Thus Gone", taking gata to be the past-participle of gam- "to go".

Selections from Free Buddhist Audio.