I'm not necessarily trying to pull your point apart, just pointing out that it's not clear-cut. Personally I've never really made my mind up, but at the moment I lean more towards a conglomeration of folk-tales and the lives of several men. I'll probably change my mind again soon.
I think you are probably remembering a (disputed) claim based on an edit made in a particular later copy that Tacitus (one of the earliest independent sources on both Christ and the early Christian community, particularly in Rome) referred to the Christian community in Rome as “Chrestians”, immediately before using the standard rendering of Jesus title as “Christus”. Even if Tacitus did use “Chrestians”, that name for the early community is attested in other sources (and even tied and used alongside Christian in some inscriptions from that community, IIRC), his reference to Christ did not use any alternate title,
https://www.ex-christian.net/topic/65072-richard-carrier-chr...