Hm... a well-kept secret, more likely. Or perhaps your world's magic is more terminally drained than mine...?

[She was mostly musing to herself, there... besides, it doesn't really matter. Mage stuff is mage stuff, Saber ain't got no time to give a shit.]

As for my name... well, consider this. In a fight to the death against a champion of the Greek, you would wish to know whether your opponent was Herakles or Achilles, would you not? Were they Achilles, your only hope would be to strike their heel... but, against Herakles, such a timid attack would likely end in your death.

A Servant's life is the key to their power; to know their name is to have the means to learn of that life. Keeping one's name secret is a Servant's way of protecting themself.

[Not the whole story, but close enough.

After a moment, she sighs, and continues.]

...I suppose it is not of utmost importance anymore, though. The life-and-death struggle is over. [...] Still, that is a decision my Master should make; as her blade, it would be selfish to dull my own edge just to satisfy my ego.

[...and, boy howdy, what an ego that is.]