Names #409, #957 · Viṣṇu Sahasranāma
प्रणवःpraṇavaḥ
Pranava — appears 2 times in the stotram, each with its own meaning
Name #409
The sacred syllable OM
From shloka 44 · chapter Narasiṃha
वैकुण्ठः पुरुषः प्राणः प्राणदः प्रणवः पृथुः ।
हिरण्यगर्भः शत्रुघ्नो व्याप्तो वायुरधोक्षजः ॥
vaikuṇṭhaḥ puruṣaḥ prāṇaḥ prāṇadaḥ praṇavaḥ pṛthuḥ
hiraṇyagarbhaḥ śatrughno vyāpto vāyuradhokṣajaḥ
Also in this shloka: vaikuṇṭhaḥ · puruṣaḥ · prāṇaḥ · prāṇadaḥ · pṛthuḥ · hiraṇyagarbhaḥ · śatrughnaḥ · vyāptaḥ · vāyuḥ · adhokṣajaḥ
Name #957
OM — the eternal syllable
From shloka 102 · chapter Kalki
आधारनिलयोऽधाता पुष्पहासः प्रजागरः ।
ऊर्ध्वगः सत्पथाचारः प्राणदः प्रणवः पणः ॥
ādhāranilayo'dhātā puṣpahāsaḥ prajāgaraḥ
ūrdhvagaḥ satpathācāraḥ prāṇadaḥ praṇavaḥ paṇaḥ
Also in this shloka: ādhāranilayaḥ · adhātā · puṣpahāsaḥ · prajāgaraḥ · ūrdhvagaḥ · satpathācāraḥ · prāṇadaḥ · paṇaḥ