கிருஷ்ணன் (Tamil) comes from Sanskrit कृष्ण, from Proto-Indo-Aryan kr̥ṣnás, from Proto-Indo-Iranian kr̥šnás, from Proto-Indo-European kr̥snós, from Proto-Indo-European kers- — black, dirty; run; to run.
கிருஷ்ணன் (Tamil): Krishna