"The Third Estate" is a question that pops up all the time and we addressed it the first week and every now and then. The Fourth Estate you refer to is in the US. We weren't going with journalism for our title. The Third Estate refers to France. Briefly, they were the left and they were neither the nobility nor the clergy (the other two estates). The estates voted amongst themselves and each estate then had one vote. The first two usually voted together. The Third demanded a head count vote (not a body count vote -- they represented more people and had more members and would win in a head count among the three estates). They took the Oath of the Tennis Court and started the French Revolution. That's the briefiest explanation.
Sometimes the issue pops up not as a question but as a 'correction' -- usely in an angry e-mail -- explaining that, "The press is the Fourth Estate, you idiots!" The ones making that claim are the idiots. We went historical with our title. Jess proposed it and Dona had a vague idea about The Third Estate. Ava and C.I. knew what it was. Jim and Ty were in the dark and asking, "Why that?" They liked the sound of it but didn't know the background. After it was explained, we all signed off on it. We think it's actually described this site in ways we weren't prepared for -- in ways we didn't expect. But that is what we've come to represent.
Those honestly wondering, we usually note the background twice a year.