Some of Jack's principal adventures are derived from the ancient Eddas and Sagas of Scandinavia.
The incident which represents Jack as having overheard a giant, upon whose hospitality he had intruded, muttering—
"Though you lodge with me this night,
You shall not see the morning light;
My club shall dash your brains out quite;"
and in which he had evaded the catastrophe by placing a log of wood in the bed, he lying quietly in a corner, while the giant furiously beat with his club the inanimate object, thinking to dash him to pieces; and the delightfully cool response of Jack to the wonder-struck giant when he beheld him safe and sound in the morning, and inquired if he had not been disturbed in the night,—"No, nothing worth mentioning, I believe a rat struck me with his tail two or three times:"—this incident is a modification of an adventure which occurred to Thor on his journey to the land of giants, and it is found in some form or other in the folk-lore of every nation in the north of Europe.
Thor, while journeying to the land of giants, met with one of that race named Skrymir. They formed a companionship, and the whole of the provisions were placed in the giant's wallet. At night, when they stopped to rest, Skrymir at once lay down and fell asleep, previously handing the wallet to Thor in order that he might refresh himself. Thor was unable to open it, and wroth with the giant for his apparent insensibility and the mode in which he had tied the knots, he seized his mighty hammer and flung it at the giant's head. Skrymir awaking, asked whether a leaf had fallen on his head, and then he fell asleep again. Thor again struck him with his hammer, and it apparently sank deep into his skull; and the giant again awoke, and asked, "Did an acorn fall on my head? How fares it with thee, Thor?" Thor, incensed beyond measure, waited until the giant again slept, and then exerting all his power, dashed his hammer at the head of the sleeping monster, into which it sank up to the handle. Skrymir, rising up, rubbed his cheek and said, "Are there any birds perched on this tree? Methought, when I awoke, some moss from the branches fell on my head."
Skrymir, distrusting Thor, had before he slept interposed a huge rock betwixt himself and the god, and upon this Thor had unwittingly exercised his strength.
The adventure in which Jack is represented as outwitting a giant in eating, by placing his food in a large leathern receptacle beneath his vesture, and then ripping it up, and defying the giant to do the same, whereupon the giant seizes a knife, plunges it into his breast and kills himself, is contained also in stories which are prevalent among the Swedes, Norwegians, Germans, Servians, and Persians.
The Swedish version is as follows:—"In the evening, when the giant and his boy were about to sup, the crone placed a large dish of porridge before them. "That would be excellent," said the boy, "if we were to try which could eat the most, father or I." The giant was ready for the trial, and they began to eat with all their might. But the boy was crafty: he had tied his wallet before his chest, and for every spoonful that entered his mouth, he let two fall into the wallet. When the giant had despatched seven bowls of porridge, he had taken his fill, and sat puffing and blowing, and unable to swallow another spoonful; but the boy continued with just as much good-will as when he began. The giant asked him how it was, that he who was so little could eat so much. "Father, I will soon show you: when I have eaten as much as I can contain, I slit up my stomach, and then I can take in as much again." Saying these words, he took a knife and ripped up the wallet, so that the porridge ran out. The giant thought this a capital plan, and that he would do the like. But when he stuck the knife in his stomach, the blood began to flow, and the end of the matter was that it proved his death."[40]
The sword of sharpness, and the cloak which rendered the wearer invisible, and by the aid of which Jack won so many important victories, are two of the principal supernatural elements in the Nibelungenlied. In this ancient legend, which contains the same tragical story as the still more ancient Scandinavian poem, the Völundar-Kvida, the sword "Balmurg" is described:—