出典:Wiktionary
From Proto-Germanic *sundijō. Cognates include Old Frisian sinde, sende, Old Saxon sundia, Old Dutch sunda, Old Norse synd, and Old High German sunta. The word may derive, ultimately, from Proto-Indo-European *h₁es- (“to be”) through a *sent-, *sont-. Latin also has an old present participle of sum in the word sons, sont- (“guilty”).