The creator of Siri is a Norwegian engineer, Kittalaus, who originally intended to call his daughter Siri. (In Norway, Siri means "a beautiful woman who leads you to the road of urban management"). He even registered the domain name siri.com.
But he and his wife gave birth to a son and the website was put on hold. Later, when Kittalaus was preparing to launch his speech recognition technology, he named it with Siri.
Later, Apple bought Siri for $200 million in April 2010. Although Jobs didn't like the name, no one could think of it better, so he always used the name.