Hades is the most recent form of his name… The meaning of Ais, Aides or Hades is most probably ‘the invisible’ or ‘the invisibility-giving’, in contrast with Helios, the visible and visible-making.
Kerényi establishes Helios as the archetypal principle of visibility and manifestation, structurally opposed to Hades as his underworld counterpart, forming the foundational polarity of Greek cosmological mythology.
, The Gods of the Greeks, 1951thesis