What does Advik mean?
A modern Sanskrit-derived name generally glossed as 'unique, one of a kind', linked to the idea of advitiya ('without a second, incomparable'). The further association with advaita ('non-duality') is thematic rather than a direct etymology.
What does Ishan mean?
From the Sanskrit ईशान (īśāna), 'ruler, master'. It is an epithet of the god Shiva, also denotes the sun and the north-eastern quarter (one of the dikpalas). A genuine, well-attested Vedic/classical term.