The names are more based on tradition and history, and to some extent the shape of the handle, the number of blades, and the combination of blade types.
A trapper, for example, usually has one or two blades of similar length, the main blade being a clip point, and the secondary a spey blade, but there are variations. If the handle is shaped like a cigar, it may be called a Cuban or cigar trapper.
It's quite a broad subject that I have been trying to learn myself.