This paper argues that obscure Homeric adjective ἀάατος is related to PIE *séh2u̯l̥, gen. sg. *sh2u̯éns ‘sun’ and goes back to a proto-form *ahāu̯ato- < *n̥seh2u̯n̥to- ‘not having sun’: the juncture ἀάατον Στυγὸς ὕδωρ (Ξ 271) can now be understood as ‘the sunless water of the Styx’. In the post-Homeric period this epithet underwent a formal renewal and is indirectly continued by ἀνάλιος / ἀνήλιος in tragedy (e.g. ἀνάλιον χέρσον (scil. of the Underworld) A. Th. 859). Under this analysis ἀάατο- < *ahāu̯ato- is best seen as an Aeolic element in the Homeric diction (which would also explain the absence of spiritus asper). While it is possible that *(a)hāu̯a to- ‘(not) having sun’ is a Proto-Greek coinage, formed from *hāu̯əl, oblique stem *hāu̯a(t)-, an expectable remodeling product of heteroclitic *séh2u̯l̥, *sh2u̯éns on the way to Greek, such athematic formation is not attested in Greek. This paper therefore argues for a possessive compound *(n̥-)seh2u̯n̥to- ‘not having sun(light)’ whose second member is a substantive *séh2u̯n̥to- ‘sunlight’ derived from adjectival *sh2un tó- ‘having sun’ by a substantivization process that involved an insertion of a new full-grade in the root in addition to the accent shift. Adj. *sh2un tó- is reflected both by Tocharian B swāñco, A swāñceṃ ‘sunbeam’ and by Proto-Germanic *sunþa ‘south’ ( < *súh2nto-, with a secondary substantivizing accent shift).
The poetic status of reconstructed *n̥séh2u̯n̥to- in Indo-European is confirmed by the existence of similar formations derived from the word for ‘sun’ in archaic Indo-Iranian texts. This paper first discusses Vedic asū́rta- (RV X, 82, 4c): asū́rtam rájas- is the Vedic term for the Underworld, exactly matching the description of the Underworld river Styx as ἀάατος (rájas- = Ἔρεβος). Secondly, it is shown that YAvestan axvarəta-, the standing epithet of xvarənah-, can be traced back to a reconstruction *n̥-s(h2)u̯el to- and interpreted as ‘not lit by the sun’, which is exactly true of xvarənah-, concealed in the waters of the sea Vourukasəm (Yt. 19, 51-59). Lastly, no less significant is another YAvestan epithet xvanuuant- ‘sunny’, associated with the heavenly waters (Y. 16, 7) and one’s immortal life: xvahe gaiiehe xvanuuatō aməṣ̌ahe (Y. 9, 1; Yt. 8, 11). Thus, in a number of Indo-European traditions there is a close association between the sun, waters, and immortality. This study of several obscure and archaic epithets from three Indo-European poetic traditions makes it possible to suggest a new interpretation of a difficult Homeric word and reveals a further aspect of Indo-European poetics.