The source of the information regarding the vocative singular in Classical Greek would be my Greek TA from my elementary Attic course. It would be better, however, if someone could find an additional source. My apologies for not having one. Medellia 03:59, 13 October 2006 (UTC)
"Despite the superficial similarity, the word is not related to Latin deus" -- this is nonsense. Of course those words cognate, hence the phrase above "Cognate with Phyrigian δεως (deōs, “to the gods”)". It is clear that Greek and Latin words are not borrowed from each other language, but those are related from common Ingo-European roots. 188.8.131.52 11:29, 16 May 2012 (UTC)
Chantraine, in his entry on 'θεός', states bluntly: 'Etymologie: Inconnue.' He then presents a few candidates, including the one given here as being established, concluding: 'finalement l'ensemble reste incertain'.
Likewise in Frisk: 'Nicht sicher erklärt.', and the same objection to linking it with *dʰ(e)h₁s: 'ē : ĕ bleibt noch zu erklären'.
Does anyone have sources stating that *dʰ(e)h₁s is now the established etymon?