In Norse mythology, Byggvir was one of Freyr's servants and the husband of Beyla. The only surviving source which mentions him and his wife is Lokasenna (the flyting of Loki). They were most-likely elves since they reside at Freyr's farm in Alfheim, and also being that Freyr is the lord of Álfheim and Lokasenna says that they were among the gods and elves. His task is to take care of the world-mill and its grist.
Loki and Byggvir have a quarrel, and Loki abuses him for telling gossip to Freyr and makes fun of his weak build: