How did the Norse ship burial ritual originate from?

Question

The Norse ship burial, according to Wikipedia:

A prominent tradition is that of the ship burial, where the deceased was laid in a boat, or a stone ship, and given grave offerings in accordance with his earthly status and profession, sometimes including sacrificed slaves. Afterwards, piles of stone and soil were usually laid on top of the remains in order to create a tumulus.

And in the movie, How to Train Your Dragon 2, the burial of the deceased chief is a ship burial, where his son lights the pyre by shooting a fire-lit arrow; and then the rest of the people (7 of them in the scene) shoots the fire arrows at the pyre, and lighting it.

So, is the ritual done like how it is depicted, or some other way?

And how did this ritual originate from, and what does it depict/it's significance?

Answer 1

Cremation with one's possessions is given as Odin's law in the Ynglinga Saga. The reasoning given is that cremation with one's possessions allow them to bring whatever was burned with them into Valhalla:

Odin established the same law in his land that had been in force in Asaland. Thus he established by law that all dead men should be burned, and their belongings laid with them upon the pile, and the ashes be cast into the sea or buried in the earth. Thus, said he, every one will come to Valhalla with the riches he had with him upon the pile; and he would also enjoy whatever he himself had buried in the earth.

An early account of such a ship burial comes from an account of Ibn Fadlan (a 10th century Arab traveler) among the Rus. It is similar in that the final burial involves the deceased placed in a ship and then burned. The ship, in this case, was aground and was not lit by arrows, however.

The reason for burning the ship is not specifically addressed, necessarily, but the implication seems to be that it is meant to accompany him to the afterlife along with the rest of his possessions. The man is cremated with numerous other possessions as well, including food, drink, an instrument, fine clothes, weapons, animals, and a slave girl. These are to be with him in the afterlife, as made clear as they instruct the to-be-sacrificed slave girl to relay a message to her deceased lord:

The girl slave who wished to be killed went here and there and into each of their tents, and the master of each tent had sexual intercourse with her and said, "Tell your lord I have done this out of love for him."

The Rus also give a brief explanation of why cremation is chosen, as opposed to burial:

"He said, 'You Arabs are fools.' " "Why?" I asked him. He said, "You take the people who are most dear to you and whom you honor most and put them into the ground where insects and worms devour them. We burn him in a moment, so that he enters Paradise at once." Then he began to laugh uproariously. When I asked why he laughed, he said, "His Lord, for love of him, has sent the wind to bring him away in an hour."

Answer 2

Kurgan Culture

Kurgans are large burial mounds that originated in Pontic steppe around 6000 BC.

The horse was domesticated in the Pontic-Caspian steppe around 3500 BC, and the chariot was likely invented by the same culture shortly thereafter.

This culture eventually became very influential, giving birth to the Indo-European language family, as the culture expanded into and merged with the populations of Europe, modern Iran, and India.

Chariot Burials

Kurgans had always had grave goods associated with the burial - weapons, pots, offerings, etc. By around 2000 BC some began to include chariots.

Nordic Bronze Age

The Corded Ware culture brought a version / descendant of Kurgan culture to Scandinavia between 3000 BC and 2000BC. This influence can be seen in burial customs like the mound at Haga.

Putting it Together

Ship Burials can be seen as a continuation of the earlier Chariot Burials, which are both subsets of Kurgan (mound) burials. This all traces back to the Proto-Indo-Europeans, whose culture became widely influential after they domesticated the horse and (likely) invented the chariot.