The syllable 'ra'comes from the eight-letteredmantraof Narayana
and the syllable 'ma' comes from the five letteredmantraof Siva.
Both are the life-giving letters (= jiiva-aksharas) of the respective mantras;
because without them the two mantras become a curse.
Without these letters, the mantra naraayanaaya becomes
na ayanaaya - meaning, not for good;
and namas-sivaaya becomes
na sivaaya - meaning, again, not for good.
Thus the word Rama combines in itself the life-giving letters
of the two most important mantrasof the Hindu religion .
The syllable 'ra' the moment it comes out of the tongue
purifies you from all the sins by the very fact that
it comes from the mantra of the protector, Naaraayana.
On the other hand,
the syllable 'ma' burns all the sins by the very fact that
it comes from the mantra of Siva, the destroyer.
This is therefore the King of all mantras,
the holy jewel of mantras,
as is rightly sung by Saint Thiagaraja,
who is one of the most famous recent historical examples of persons
who attained the jivan-miukti stage
- the released stage even while alive -
by the sheer repetition of the Rama name.