摂政

/sepuɕʲau/ → /seɸuɕʲau/ → /seuɕʲau/ → /ɕʲɔːɕʲɔː/ → /ɕʲoːɕʲoː/

From Middle Chinese compound 攝政 (syep tsyeng^H, literally “grasp + government”). Compare modern Mandarin 攝政／摄政 (shèzhèng, “to act as a regent”).

The goon, so likely the reading as first borrowed.

• On’yomi: Goon
  • IPA^(key): [ɕo̞ːɕo̞ː]

摂政 (shinjitai kanji, kyūjitai kanji 攝政, hiragana しょうしょう, rōmaji shōshō, historical hiragana せふしやう)

1. (archaic) the chief advisor to the emperor, similar to a viceroy or vizier

• (viceroy): 関白 (かんぱく) (kanpaku)

Shift in reading of shōshō above, using the kan'yōyomi of setsu for the 摂 character.

• Kan’yōyomi
  • (Tokyo) せ​っしょー [séꜜsshòò] (Atamadaka – [1])[1]
  • (Tokyo) せっしょー [sèsshóó] (Heiban – [0])[1]
  • IPA^(key): [se̞ɕːo̞ː]

摂政 (shinjitai kanji, kyūjitai kanji 攝政, hiragana せっしょう, rōmaji sesshō, historical hiragana せつしやう)

1. a regent: one who rules in the place of a monarch because the monarch is too young, absent, or disabled
2. regency: the position or station of a regent
3. (archaic) the chief advisor to the emperor, similar to a viceroy or vizier

• (viceroy): 関白 (かんぱく) (kanpaku)

• 摂 (せっ)政 (しょう)皇太子 (こうたいし) (sesshō kōtaishi): the Prince Regent

• 1988, 国語大辞典（新装版） (Kokugo Dai Jiten, Revised Edition) (in Japanese), Tōkyō: Shogakukan