What does Shivansh mean?
A modern compound of Shiva and amsha (अंश, 'portion/part'), read as 'a part of Lord Shiva'. A contemporary devotional coinage rather than a classically attested 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.