I have used the nickname "Tertiumquid" probably around 10 years or so. I picked it randomly out of a Latin glossary in the back of book when trying to pick a user name for an Internet service provider. I am the original Tertiumquid. When I began using it, I doubt anyone was using it.
Do not be fooled by this blog entry:
"Tertium Quid details a touching aspect of grace in his life after becoming Catholic. Check it out."
There is also a band that uses the name, as well as a poet, and bunch of other people as well. In regards to someone with this nickname swimming the Tiber, well, let's just say I would buy the band's CD and listen to the poet before I grant someone well-wishes for embracing sola ecclesia.