In regards to Sera's mocking of Corypheus's name...
There's also something historically and mythically powerful about names and how we use them. Names define us. Names give and take away power through definition and redefining under new light. Names and the refusal to use names can represent fear or lack of fear, respect or lack of respect, and to use a name or not use a name out of defiance is a symbolic important gesture towards combating it.
If you read the Harry Potter books, this is illustrated in the several stages of fear and intimidation from The Dark Lord, He-Who-Shall-Not-Be-Named, aka Lord Voldemort, aka Tom Riddle. The general populace that fears him, won't even utter his name out of terror. The resistance that defies him does not fear to name him, first as Voldemort, then as the truth of his origins come to light, as Tom Riddle.
Ancient human history amongst aboriginal tribes, islander tribes, American Indians, and many more ancient cultures have also recognized the power of names, and the power of giving a new name to the object of terror or fear. In human societies across Europe to Asia, clowns and fools have practiced this since antiquity. To name something is to have power over it, to give it a new name that takes away the fear and majesty something previously had, is to replace those emotions and impressions with laughter and bravery. This is what Sera practices, even if she's not entirely conscious of it, she plays the part of the jester, the clown, the fool, and both names and then renames the Foe because it takes away the fear and reduces them in the eyes of all to something that can be fought, something that can be defied, and something that can be beaten and laughed at.