What does Atharv mean?
From Sanskrit atharvan (अथर्वन्), the name of the Atharvaveda and of the ancient sage traditionally said to be the first priest of fire. Commonly taken to mean 'knowledge' or evokes the Vedic fire-priest.
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.