What does Arjun mean?
From Sanskrit arjuna (अर्जुन), 'white, bright, silvery, clear'. Best known as the heroic third Pandava prince and Krishna's friend in the Mahabharata; the literal root sense is 'shining/white' rather than 'warrior'.
What does Reyansh mean?
A modern coinage usually read as 'ray of light', often analysed as 'ray' plus the Sanskrit amsha (अंश, 'portion/part'), giving a devotional reading 'a part of Vishnu'. The Vishnu link is an interpretation built on amsha rather than a documented classical meaning.