Hmmm.... I hadn't considered players making checking against my Bluff skill. I more meant hiding the fear from the NPC prisoner sorts. Most of my players generally just decided if they notice or not no matter what they rolled :) Mind you, I think I was the only one in our group that casually walked into a trap because I deemed my character wouldn't know about it. They thought I was crazy. Clearly our players here are better than those at my old table.

As for TN, that's used in several other systems. It refers to "Target Number" and yes, is identical to "Difficulty Class". I often use terms interchangeably from other systems. Sorry about that.