Late 19th century. From classical Latin sexāgēnī sixty each + -al. In both quotations, sexagenal cycle renders a Japanese word for the sexagenary cycle, probably either eto, or jikkanjūnishi, or kanshi.
Definition of sexagenal in US English:
sexagenal
adjective
rare
= sexagenary.
Origin
Late 19th century. From classical Latin sexāgēnī sixty each + -al. In both quotations, sexagenal cycle renders a Japanese word for the sexagenary cycle, probably either eto, or jikkanjūnishi, or kanshi.