According to Bulbapedia, characters that debuted after Generation 2 have titles like “the charmer” and “the conqueror”. However, I have never seen anything in the books themselves that refer to the characters with such titles.
Pleaselog inorregisterto add a comment.
(Basically, he gets the title from the Professor.)
Okay, the rest of the titles were just given to the characters based on the skills they each had, for e.g. Ruby has the title of “Charmer” because of he cares about his Pokemon looking beautiful and Charming. These titles probably show up in the re-introduction to the characters pages which are the first few pages in each manga volume. (Those pages also give you a summary on what events have occurred.)