It's Yet Another Magic Word, only a bit complicated... you have to enter each word on a separate line by itself, in the proper order. In other words:

fee
fie
foe
foo

(Yes, "foo." Just for fun, try "fee fie foe fum" and see what happens.)

What does it do? You can say the magic words in the room that the eggs are in, or in another room, but in each case nothing seems to happen. But try picking up the eggs and taking them to another room, and then saying the magic words. Then go back to the room the eggs were originally in. The magic words teleport the eggs to the room in which you find them originally.

Gee. Does that give you an idea on one way you might cheat the Troll at the Troll Bridge?