神酒

Possibly from Middle Chinese compound 神酒 (ʑiɪn t͡sɨu^X, literally “god + wine”).

Alternatively, coined in Japan of Middle Chinese-derived elements, as a compound of 神 (shin, “god, spirit”) +‎ 酒 (shu, “wine, liquor, alcohol”).

The individual character readings are kan'on shin + goon shu, suggesting either an innovation in the reading after borrowing, or a Japanese coinage.

• (Tokyo) し​んしゅ [shíꜜǹshù] (Atamadaka – [1])[1]
• (Tokyo) しんしゅ [shìńshú] (Heiban – [0])[1]
• IPA^(key): [ɕĩɰ̃ɕɨᵝ]

神(しん)酒(しゅ) • (shinshu) 

1. sacramental sake used in a Shinto ceremony
2. ambrosia, nectar

• 聖酒(せいしゅ) (seishu): sacramental sake, sacramental wine
• アンブロシア (anburoshia): ambrosia
• ネクター (nekutā): nectar of the gods

From Old Japanese 御酒 (mi₁ki₁). Appears in the Kojiki of 712 CE. In turn, from Proto-Japonic *mi-ki.

Compound of 神 (mi, “honorific prefix used in spiritual contexts”) +‎ 酒 (ki, “wine, liquor, alcohol”, ancient root, not found in many words).[1][2][3]

• (Tokyo) みき [mìkí] (Heiban – [0])[1]
• (Tokyo) み​き [míꜜkì] (Atamadaka – [1])[1]
• IPA^(key): [mʲikʲi]

神(み)酒(き) • (miki) 

1. sacramental sake used in a Shinto ceremony
2. ambrosia, nectar

In Shinto contexts, often prefixed with the honorific o- as 御神酒, 大御酒 (omiki), or ō- “great” as 大神酒 (ōmiki).

• 聖酒(せいしゅ) (seishu): sacramental sake, sacramental wine
• アンブロシア (anburoshia): ambrosia
• ネクター (nekutā): nectar of the gods

From Old Japanese. Appears in the Man'yōshū of 759 CE. Compound of 神 (mi, “honorific prefix used in spiritual contexts”) +‎ わ (wa, a morpheme of uncertain derivation).[1][2][3] The final wa may be related to 泡 (awa, “bubble”) in reference to the bubbles of fermentation (compare 泡盛 (awamori, “Okinawan rice-based strong spirits”, literally “lots of bubbles”)), but this is only speculation.

• IPA^(key): [mʲiɰᵝa̠]

神(み)酒(わ) • (miwa) 

1. (obsolete) sacramental sake used in a Shinto ceremony
2. (obsolete) ambrosia, nectar

The miwa reading appears to be obsolete.