The word rama literally means “pleasure.” With a long initial “a,” rāma, it means “pleaser and enjoyer” – a “lover” in the romantic and erotic sense. It is a name for the god of eros, kāma-deva, and is used amongst commoners to denote any extremely seductive and attractive man or woman.
The words rāma and krishna form a natural pair, because krishna indicates the attraction of consciousness, and rāma indicates the thing consciousness is attracted to: pleasure! It also indicates the result of being attracted to krishna: pleasure.
If krishna refers to Brahman – the self-sustaining, effortlessly manifest effortless consciousness – then rāma refers to the bliss of that carefree existence: brahmānanda – nirvāṇa.
If krishna refers to Paramātmā – the effortless manifestor of all consciousness – then rāma refers to śānta-rasa the joyful experience of seeing all things as equally divine and thus feeling effortlessly peaceful and satisfied.
If krishna refers to Bhagavān – the epitome of effortlessly joyful personal consciousness – then rāma refers to devotional sentiment, bhakti-rasa, the feeling of affection and admiration for that Supreme Person.
Some say that the entire mahāmantra is about Bhagavān and the word krishna refers to one manifestation of Bhagavān, the Gopa of Vṛndāvana, but Rāma refers to a different manifestation, either Paraśū-rāma, Rāma-chandra, or Bala-rāma. There is nothing incorrect in this view, but it does not allow the deepest understanding of the mahāmantra to unfold. It is not wrong, but it is not the best understanding either.
The best understanding is that the three nouns of the mantra name and describe the same entity – the being who is the origin of all manifestations of Bhagavān, Paramātmā, and Brahman. That entity is the primeval erotic principle in person – the transcendent, self-manifest kāma-deva at the root of all existence.
By the name krishna he “pulls” and “attracts” us. Then, by the name rāma he enjoys us… and thus delights us.