Naming was changed in version 2.59 (number is shown at the bottom of the page 'Info/Guides and documents').
Currently the naming goes like this:
First there is one letter to indicate the waypoint type: A and B are of course the start and end points of a route. 1, 2, 3... Intermediate waypoints get just numbers P = A location cache
Next letter Q is added if it's a waypoint where you can find the answer to the control question.
Then comes the cache name (except that intermediate waypoints only get a number. Or number + 'Q').
Examples: 'B K Mountain road' = B-point of route cache 'Mountain Road' '3' = It's the third intermediate waypoint of some route cache. 'P Tower' = Location cache 'Tower' (no control question). 'P K Tower' = Location cache 'Tower' with a control question.