It is believed that Shuto originally came from salted fish guts, made and eaten by fishermen and processors who made it from the large amount of guts removed when they made namaribushi (boiled and half-dried bonito).
もともとは生利節を製造する際に大量に出る内臓を、漁師や加工業者が塩辛にして食べていたものが始まりであると言われている。