Hyperion was a Titan, the son of Uranus and Gaia and the father of Helios (with whom he is often identified). His name means 'going over', 'one who walks on high', from hyper, 'over' and ion, 'going'.

This is obviously a good name for a giant who 'walks tall', but the traditional association of the name is with the sun, which 'goes over'. (Homer actually calls the sun Hyperion in Book 19 of the Iliad.)