What does Dev mean?
From Sanskrit deva (देव), 'god, deity, divine one', from a root meaning 'to shine'. A simple, ancient word meaning 'divine'.
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.