In Norse cosmology, Asgard, the land of the Aesir gods, and Jotunheim, the land of the giants, are separated by a the Iving River, which never freezes over, making it very difficult to cross. Since the giants and the gods are always fighting with each other, the gods also decided to build a huge wall around Asgard to protect it, making it very difficult for giants to cross into Asgard, and vice-versa. (Psst. You can learn more about the wall in "The Walling of Asgard.") That's why Freyja's feather dress is such a huge help to Loki when he travels to Jotunheim in search of Thor's hammer. It allows him to soar right over all those pesky barriers. Similarly, Thor's chariot enables him and Loki to reach Jotunheim much more easily than they ever could on foot.
Once Thrym sees his "bride" coming, he orders his servants to put straw on the benches, a move that symbolizes decorating the halls for a wedding feast. Very specific things must occur at a Norse wedding feast. People have to stuff their faces, which is why there's enough food at this feast for Thor to eat an entire ox, eight salmon, three barrels of mead, and an entire wedding cake. Also, during the feast, the bride and groom exchange gifts. The bride's family provides her with a "bridal fee," usually in the form of gold.
Thrym's sister demands the bridal fee from "Freyja" in this story, a moment that seems to remind Thrym that he owes his bride a wedding gift. He's already promised the gods that this gift will be Thor's hammer. The irony in this story, of course, is that putting his gift in the lap of his "bride" is exactly what brings Thrym's marriage to "Freyja" to an end. "Thrymskvitha," the poem about the theft of Thor's hammer, characterizes the blows that Thor lands once his hammer's returned to him as the "bridal fee" Thrym's sister has demanded. In this way it uses the conventions of the wedding feast to produce humor in what is otherwise a seriously gross and disturbing moment.