"Sunacchi" is an abbreviation for a phrase translating to "Throw Away Your Name and Wits" (〝名前〟を捨てろ 〝知恵〟を捨てろ "Namae" o Sutero, "Chie" o Sutero?). The VIZ translation uses the phrase "Surrender Your Name and Be as a Child".
When Ashura Doji and his comrades were children around 50 years before the present day, they used the cry of "Sunacchi" as a form of encouragement to partake in a "test of courage", which for them was cliff diving into the ocean. The cry encouraged them to stop thinking and worrying about the danger they may be in and just take action. Ashura's comrades gave that cry once again 10 years before the present, when they set off in an ultimately doomed journey to Onigashima to take down Kaido. It appears to be considered uncouth language used by commoners, as Kikunojo told Kozuki Momonosuke that it was improper for him, as a daimyo's son and the heir to the shogunate, to use.
The cry was carried over to the East Blue by Shimotsuki Kozaburo and his comrades when they founded Shimotsuki Village 55 years ago, and Roronoa Zoro heard Kozaburo using it while training around a decade ago. He never used it, but told Momonosuke about it to energize the latter in his sword training, saying that it would strengthen his heart when his courage falters.
- The Wano Country version of "Sunacchi" is written differently from the East Blue version that Zoro and Momonosuke use; the Wano version is written in kanji with katakana furigana, while the East Blue version is written in hiragana (すなっち).
- ↑ 1.0 1.1 1.2 1.3 One Piece Manga — Vol. 93 Chapter 934 (p. 7), Momonosuke first mentions sunacchi.
- ↑ 2.0 2.1 SBS One Piece Manga — Vol. 96 (p. 80), Oda reveals the connections between Wano and Shimotsuki Village.
- ↑ 3.0 3.1 One Piece Manga — Vol. 94 Chapter 950 (p. 11).
- ↑ One Piece Manga — Vol. 95 Chapter 955 (p. 9).