Note that when he used the word DarkTor, everyone instantly know what is he talking about. That is a functionality of a good name.

Can I use the word "Tor" as part of the name of my product or my domain name?

Please don't use Tor in your product name or domain name. Instead, find a name that will accurately identify your products or services. Remember that our goal is to make sure that people aren't confused about whether your product or project is made or endorsed by The Tor Project. Creating a new brand that incorporates the Tor brand is likely to lead to confusion, and commercial confusion is a sign of trademark infringement.