Kojiki: Records of Ancient Matters · Section 159
Emperor Yū-riyaku (Part X.—The Mound of the Metal Spade)
159.1Again when the Heavenly Sovereign made a progress to Kasuga to wed Princess Wodo, daughter of the Grandee Satsuki of Wani, a maiden met him by the way, and forthwith seeing the Imperial progress, ran and hid on the side of a mound. So he composed an august Song. That august Song said: “Oh! the mound where the maiden is hiding! Oh for five hundred metal spades! then might [we] dig her out!”
159.2So that mound was called by the name of the Mound of the Metal Spade.