TTL = Ticketing Time Limit - a requirement to ensure the sector(s) are fully accounted for by a particular time/date.
PNR = well let's call that the booking reference - a wraparound that emcompasses all the parts of a booking under a single reference. Usually a flight ticket but it can include hotels and train tickets and Disney trips. It stands for Passenger Name Record but I have to look it up every time, it's not a good way of looking at it. The argument above is where / when did it kick in for your scenario.

There is another one in this area, and I think you may have been hit by it, PTL - Payment Time Limit. I'm no expert on Cathay but a big downside of transfering miles between different pools is that you risk this sort of scenario.