What does Dhruv mean?
From the Sanskrit ध्रुव (dhruva), 'fixed, firm, immovable, constant'; also the name of the Pole Star and of the boy-devotee Dhruva in the Puranas, who became the unwavering North Star.
What does Aarush mean?
From Sanskrit arusha (आरुष), 'reddish, red of dawn', commonly glossed as 'the first ray of the sun'. The 'red/dawn' sense is the attested one; 'first ray of sun' is the popular reading.