The leather sleeve covering the sword originates from a tool used by samurai when they traveled a long distance, used to protect the sheath from dirt and damage by placing the tool along the whole length of the sheath; the wrinkle on the surface of the tool resembles the skin of a toad, and as such it is called hikihada (skin of toad).
上に被せる革筒は、もともと遠出する武家が鞘全体へ被せて汚れや損傷などを防いだ道具（表面の皺が蟇蛙に似ていたため蟇肌と呼ばれる）から始まっている。