Probably because it was known that sesame enhances the liver's functioning, reishu (sweet half sake) darkened with black sesame powder was used to cure hangovers later in the Muromachi period.
後にこれに倣って醴酒を、ゴマの肝臓機能強化を知ってか悪酔い止めにと黒ゴマ粉で濁したものが室町時代に用いられた。