Canto 3 -
Araṇya-kāṇḍa
Chapter 73: Kabandha Requests Śrī Rāma to Visit Śabarī
Text 3.73.30

ऋश्यमूकश्च पम्पायाः पुरस्तात्पुष्पितद्रुमः।
सुदुःखारोहणश्चैव शिशुनागाभिरक्षितः॥

ṛśyamūkaś ca pampāyāḥ purastāt puṣpita-drumaḥ
suduḥkhārohaṇaś caiva śiśu-nāgābhirakṣitaḥ

ṛśyamūkaḥ ca = is [Mount] Ṛśyamūka; pampāyāḥ = Pampā; purastāt = in front of; puṣpita-drumaḥ = flowering trees grow on it; suduḥkha-ārohaṇaḥ = it is very painful to climb over it; ca eva = and; śiśu-nāga-abhirakṣitaḥ = because it is protected by baby elephants.

In front of Pampā is [Mount] Ṛśyamūka. Flowering trees grow on it and it is very difficult to climb over it because it is protected by baby elephants.

Ṛśyamūka refers to that place where ṛśyas, a species of deer, becomes silent.1

1 Rāmāyaṇa-bhāva-dīpa: ṛśyāḥ mṛga-viśeṣāḥ mūkāḥ niḥśabdāḥ bhavanti yasmin saḥ ṛśyamūkaḥ.