What does Raja mean?
From Sanskrit 'rajan' (nominative 'raja'), meaning 'king', ultimately from a Proto-Indo-European root meaning 'to rule, to straighten'. (Note: the identically-spelled Arabic 'Raja' is an unrelated feminine name meaning 'hope'.)
What does Ranbir mean?
A Sanskrit/Hindi compound of rana (रण, 'battle') and vira (वीर, 'hero, brave one'), giving 'a warrior brave in battle'.