I've used unix-like OS's for 28 years and I don't remember coming across it as a password.
It is a common username (see: https://en.wikipedia.org/wiki/Toor_(Unix) ), the machine I am typing this on has it.
It was the default password for the root user in Kali Linux for a while.
It was the default password for the root user in Kali Linux for a while.