According to Dixon-Kennedy, p. 143 (following Kerényi 1951, p. 230) says "...his name means 'the unseen', a direct contrast to his brother Zeus, who was originally seen to represent the brightness of day". Ivanov, p. 284, citing Beekes 1998, pp. 17–19, notes that derivation of Hades from a proposed *som wid- is semantically untenable; see also Beekes 2009, p. 34.
