Grinning Aoe/Origin

Japanese legend has it that a demon in the shape of a woman (in some tellings, she was with her young son as well) was prowling about at night, smiling widely and insanely. A samurai encountered this ghost one evening, and when she approached, he quickly took out his sword and beheaded her -- instinctively, and correctly, guessing what she truly was. When he lodged for the night and returned in the morning to the location of the encounter, he found a stone lantern (or statue) that had been cut through cleanly as if by a sword. From then on, the samurai's sword was bestowed the name of Nikkari Aoe, or "Grinning Aoe."


 * (Nikkari refers to the "grinning" expression of the ghost, and I believe Aoe refers to the brand of the sword or the name of the swordsmith).