Chapter1- Ślokās 30,*31
gāṇḍīvaṃ sramsate hastāt tvak caiva paridahyate |
na ca śaknomy-avasthātuṃ bhramatīva ca me manaḥ || 30 ||
nimittāni ca paśyāmi viparītāni keśava |
(1.30 - *1.31)
keśava- O Keśava!; gāṇḍīvaṃ- my bow named Gāṇḍīva; sramsate- is slipping; hastāt- from the hand; tvak ca eva- and (my) skin too; paridahyate- is burning all over; na śaknomy- I am unable to; avasthātuṃ ca- even stand steadily; me manaḥ ca- and my mind; bhramati iva- appears to be whirling; paśyāmi- I am seeing; viparītāni nimittāni ca- omens of misfortune too;
Purport
Arjuna continued, “O Keśava! The bow Gāndiva is slipping from my hand and my skin is burning all over. I am unable to remain steady and my mind appears to be whirling. I see inauspicious omens too.”
Keśava Arjuna addressed Bhagawān as Keśava in this śloka. Bhagawān is called Keśava as HE has exquisite curls (keśa) and is the killer of the demon Kesi.
ka iti brahmaṇo nām īśohaṃ sarvadehinām | āvāṃ tavāṃge saṃbhūtau tasmāt keśavanāmavān (kaḥ is the name for Brahma. I (Śiva) am the Īśwara (Lord) of all those who are in body consciousness. Both of us have come from your body. Hence you got the name Keśava.) From this statement made by Rudra himself in Harivaṃśaṃ, we come to know that HE is called Keśavā as HE is the cause of the existence of Brahma and Rudra.
By addressing Bhagawān as Keśava, Arjuna is pleading,' O Keśavā! You are the cause of the existence of even Brahma and Rudra. Please support me too.'