"kartavya" is a word founded from the Sanskrit origin but has totally unrelated meanings in english. In sanskrit it means "duty". In English, the word is an informal addressing made to someone you like, love. Or to someone who you find
intelligent, or "classy"/"dude", the Best.
The word, pronounced as "care-tev-aa" is commonly used in
the northern parts of USA and in
California and the Atlantic islands.