According to Tamil Saint Tirumular, the following is the definition of these epithets.Eka-varNa - dvi-varNa - tri-varNa
ஓரெழுத்தாலே உலகெங்குந் தானாகி OrezhuttAlE ulagengun tAnAgi
ஈரெழுத்தாலே இசைந்திங் கிருவராய் IrezhuttAlE isaindingiruvarAi
மூவெழுத்தாலே முளைக்கின்ற சோதியை mUvezhuttAlE muLaikkinRa sOdiyai
மாவெழுத்தாலே மயக்கமே உற்றதே (885) mAvezhuttAlE mayakkamE uTradE
Letter A - U - M
By one letter, A, He all worlds became;
By two letters (A and U), He the Two became - Siva and Sakti;
By three letters (A, U, M) He the Light (jnAna) became;
By letter M was Maya ushered in.
From the One Letter mantra, Aum (Pranava), that is nAda, all the worlds devolved.
The two letters A and U became Siva and Sakti, and the letter M became mAyA.
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(Aum consists of three letters 'A', 'U' and 'M'. But as the three letters are always evoked together as Aum, it is also known as One letter Mantra.
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Mular treats Aum (instead of natural Hamsa) as the ajapa. In Sanskrit, ordinarily OM is treated as mono-syllable; but as Panini has pointed out, the combination of a and u in this word, as an exception to the general rule, is to be pronounced 'au' a diphthong. This is the general rule in Tamil language.
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(Translation and notes by Dr B Natarajan)