Infact in the same Maha-bharata (12.328.1 up to 6) we find a description of the multicolored rays emanating from the Lord body seen by Narada Muni, and after in the same chapter number 328 Sri Krishna states the following:
amsavo ye prakasante
mama te kesa-samjnitah
sarvajna kesavam tasman
mam ahur muni sattamah
“The effulgent rays that emanate from me are called kesa. Therefore the best of sages who know everything call me Kesava.”
Another meaning is,
worshiped (va, vandana) by Ka (Brahma) and Isa (Siva)
Ka+isa+va is Kesava.
Another meaning is
“He who has beautiful long hairs”.
In the Bhagavad Gita Arjuna uses the name Kesava for Krishna a number of times, referring to him as the ‘Killer of the Keshi demon’:
“I am now unable to stand here any longer. I am forgetting myself, and my mind is reeling. I see only causes of misfortune, O Kesava, killer of the Keśī demon.”
(Bhagavad Gita 1.30).
The demon Keshi, in the form of a horse, was sent by Kamsa to kill Krishna but was overpowered and slain
(Vishnu Purana 5.15-16).
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