Doubtful that you'll see this after 14 years, but for the benefit of anyone else wondering... I believe it has to do with the gap that the play hits. The counter deuce hit outside the tackle (the second man on the line of scrimmage), while the trey hit outside the tight end (the third man on the line of scrimmage); if you ran deuce to a tight end side, the tight end - rather than joining the strong side of line in downblocking to build the wall at the point of attack - would arc around. The TE would end up blocking an outside backer or safety, and his arc steps - similar in appearance to the reach step used on outside zone/stretch runs - might influence the man in the C gap (the kickout man) to follow him, resulting in a brutal, blindside kickout. Or, if the C gap player watched the tackle to his inside block down, he might turn towards the TE expecting him to block down (as he would on counter trey) - again, resulting in that player getting blindsided on the kickout.
The terms "duece" and "trey" were the terms that were used around the time of these play's conception; nowadays the terminology is a bit different. You don't really hear counter deuce. "Counter" is a general term for any play where the playside lineman build a wall at the point of attack, the backside guard kicks out the contain man, and another player leads through on the playside linebacker. You would most likely hear a "counter deuce" to a tight end side referred to as an "influence trap". The term "counter trey", while still in use, no longer refers to the gap that it hits, but to who is doing the blocking; while "counter" generally refers to the backside guard pulling and kicking out with a fullback leading on the playside linebacker, "counter trey" refers to a play where the backside tackle pulls and leads through, rather than the fullback.
Correction; after doing some digging, it seems I'm remembering wrong. Trey and Deuce originally referred to where the double teams take place on the play side; trey meant it occurred in the C gap (TE and tackle), deuce in the B gap (tackle and guard), and there was even an ace that occurred in the A gap, between the center and guard.