Ēka-śaraṇam (literally, 'one sole refuge') denotes the radical non-duality of the prapanna's orientation — the state in which the surrendered soul has no residual reliance on any other support whatsoever: not on one's own effort, not on the intercession of other deities, not on the merits of previous karma, not on any upāya other than Bhagavān Himself. This is the lived meaning of ananya-śaraṇatva (having no other refuge) and ananya-gatitvam (having no other course), which are the two defining marks of the prapanna described in the Śrī Vaiṣṇava rahasyam literature.
The Āchāryas distinguish ēka-śaraṇam carefully from mere monotheism or devotional exclusivism. It is not simply a preference for Viṣṇu over other gods; it is the recognition, arising from tattva-jñāna (knowledge of the true nature of things), that only Bhagavān possesses the capacity, the sovereignty, and the unconditional compassion to grant mokṣa. Other deities, even the most exalted, are themselves śeṣa (belonging to Bhagavān) and paratantra (dependent on Him); they cannot serve as ultimate refuges. The namaḥ component of the Tirumantram is specifically interpreted by Piḷḷai Lōkācāryar in the Mumukṣuppadi as the ātmā's renunciation of all such alternative refuges — the definitive declaration of ēka-śaraṇam.
The practical fruit of ēka-śaraṇam is fearlessness (abhayam). The prapanna who has truly taken Bhagavān as the sole refuge no longer trembles before kālan (death), no longer anxious about the outcome, no longer uncertain about protection — for Bhagavān Himself has given the assurance of mā śucaḥ ('do not grieve') in the Carama Ślokam of the Bhagavad Gītā. This fearlessness is not born of the prapanna's own strength but of the Lord's sovereign and unconditional promise to protect those who have surrendered to Him alone.