I agree, Ian. How can a person "let the words be what they are"? A deer cannot put a knight on her back and bury him.

When I think about it, it would be almost as unlikely for a pregnant woman to go onto a field, hoist up a dead knight, dig a big-enough grave and bury him, all by herself.

If he had been a wandering knight slain in single combat, then she wouldn't know where he was. If he had been slain in battle, the thought of a pregnant woman, presumably of the nobility, making her way through the bodies while avoiding the scavengers (animal and human) boggles the mind.

No, there is a hidden magic spell at the heart of this sing. That's why people are still singing it.