"Cortana is an intelligent personal assistant on Windows Phone 8.1. [2] Its name comes from Cortana, the artificial intelligence character in the Halo series, with Jen Taylor, the character's voice actress, returning to voice the personal assistant's US-specific version.[3]"
http://en.wikipedia.org/wiki/Microsoft_Cortana
"Cortana is an intelligent personal assistant on Windows Phone 8.1. [2] Its name comes from Cortana, the artificial intelligence character in the Halo series, with Jen Taylor, the character's voice actress, returning to voice the personal assistant's US-specific version.[3]"