Shloka 5.38.68
अभिज्ञानप्रदानम् — The Token of Recognition (Chūḍāmaṇi) and the Crow Episode Recalled
रावणेनोपरुद्धां मां निकृत्य पापकर्मणा।त्रातुमर्हसि वीर त्वं पातालादिव कौशिकीम्।।5.38.68।।
rāvaṇenoparuddhāṃ māṃ nikṛtya pāpakarmaṇā |
trātumarhasi vīra tvaṃ pātālādiva kauśikīm ||
O hero, it befits you to rescue me—humiliated and imprisoned by the sinful Rāvaṇa—just as Kauśikī, the Earth, was rescued from the netherworld.
"O heroic Rama! just as Kausik was rescued from the underworld it behoves you to deliver me from imprisonment of wicked Ravana".
In this context, Kausiki is widely interpreted by commentators as the Earth (Bhudevi) or the divine prosperity (Lakshmi/Indra's Shakti) that was submerged in the netherworld and subsequently rescued, serving as a simile for Sita's situation.
By addressing him as 'Vira', Sita is invoking Rama's martial duty (Kshatriya Dharma) and valor, reminding him that it is the obligation of a hero to destroy evil (Ravana) and rescue the oppressed.