Like trees of konotegashiwa (a specie of tree that was often used as a metaphor of two-sided person) in Mt. Nara, which have two faces, these means flatter two sides ("Manyoshu" Vol. 16-3836).
奈良山の児の手柏の両面にかにもかくにも佞人の徒（『万葉集』（巻16-3836））