What does Neel mean?
From the Sanskrit नील (nīla), 'dark blue, indigo, sapphire'. A genuine classical colour word, also the root of 'neelam' (sapphire). Note: the similar-looking English/Irish name Neil (from Gaelic Niall) is a separate, unrelated name.
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.