It's been so long since she's heard her name, or even her proper title — in Calormen, she is Rabadash's wife, his princess, or the barbarian queen, and because of that, people (even her husband) avoid speaking to her directly— it's been so long that she's forgotten what her name sounds like, spoken by anyone.

But Susan grew up in a land of magic, and she knows the power that names have — it's best that they don't name her, because that would give them even more power over her than they have now, and Susan keeps what power she can, storing it up for when she needs it, for when it's time to make her move

When that time comes, she will know, because she will hear it ringing in her ears — "All hail Queen Susan the Gentle" and she will escape.