Seth's Surname in S03E02 Seth

I have been rewatching this episode the other day, which reminded me of one part of this that I never understood.

When the ATF special agent is explains Seth, the cult and the ATF's operation observing them. O'Neill mouths 'Fargough' to Daniel just after the ATF special agent mentions his full name. Daniel seems confused by it, as does O'Neill. I am totally oblivious as to what this even is.

Is this some kind of reference to something that happened in the US that is similar to this? It bugs me every time I see this episode.