It seems that shio-konbu boiled with soy sauce was cooked using L. religiosa in the Sengoku period (period of warring states), which was served in the ceremony to go into a battle as lucky foods along with dried chestnuts, because the sound of konbu (kelp) made people think of joy (joy is "yoro-kobu" in Japanese, "yoro-kobu" and "yoro-konbu" have similar sounds) and dried chestnuts made them think of victory (dried chestnuts are called "kachi-guri" [literally, victory and chestnut] in Japanese).
戦国時代の出陣の際、勝ち栗や喜ぶなどの縁起を担いだ出陣式に醤油で炊かれた塩昆布は細目昆布を醤油で煮込んだものと思われる。