Well, she got her nickname when we were traveling to the Carolinas for Thanksgiving. We were trying to find a good name for the voice on the nav, and hubby thought that it should be Vanessa and I liked Savannah (it's a van, after all... also van is nav backwards). As a compromise, he calls her Vanna, and I call her Savannah. She seems happy, regardless.
BTW, did you ever notice that there are two different female voices on the nav? At least on ours, we noticed two different voices and main voice sounds happier than the other one, which, if I remember right, does the voice recognition input. (After spending over 40 hours traveling, you tend to notice those things.)