The most important aspect of the virgin martyr's life is that she dies for her faith. It is through this extreme but highly symbolic action that the saint signals her holiness to the world. Cecilia does this through other actions too – like remaining a virgin, converting many pagans, and never ceasing to pray and keep Christ's passion in mind – but these actions are all preparation for the most definitive one, her death. Beyond signaling her sanctity, Cecilia's instruction of her converts and showdown with Almachius testify to her education, confidence, and eloquence in her faith. As for the other characters in the tale, they, too testify to the strength of their faith through their martyrdom and the conversions they carry out.
The narrator uses a long explication of Cecilia's name to give us direct characterization of Cecilia in her Prologue. She does this by implying that the various meanings of Cecilia's name are related to character traits that Cecilia possesses. For example, the narrator claims that in English, Cecilia means "hevenes lilie," and since the lily is a symbol of chastity, she says that Cecilia has this name because of her "pure chaastness of virginitee" (88-90). Another possible definition of Cecilia is "the wey to blynde," which the narrator interprets as signifying Cecilia's good example and good teaching, through which she showed "blind" pagans a way to God. Cecilia might also mean lack of blindness, indicating Cecilia's spiritual wisdom.
Why is the Second Nun so interested in the meanings of Cecilia's name? Well, like many medieval people, she probably believes that a thing's name reveals something really important about the character of that thing. This idea comes from a perception of all of God's work in the world as meaningful, so that the name he happens to ordain for Cecilia is a 'message' to other Christians about her character. It also relates to a popular late classical encyclopedic work, the Etymologiae of Isidore of Seville. In this book, Isidore studied the origins of words, and their meanings, as a way of learning about the world. His explanation of the Latin name of wolf, vulpes, as originating from the fact that wolves are volupes, or shifty on their feet, betrays a similar impulse to our narrator's to connect the meanings of a name to the character of the one so named.