Several theories have been told as regard to the name of this fundoshi: it came from a gift from the medicine distributors from Ecchu Toyama region (they distributed medicines across the country, placing medicines at individual homes, and collecting the money for the used amount when they visit next time); it came from Tadaoki HOSOKAWA because he invented this type of fundoshi and his official title was Ecchu no kami (a govonor of Ecchu Province).
名前の由来には越中富山の置き薬の景品で全国に普及したことに由来する説や、越中守だった細川忠興が考案者とする説など、複数の説がある。