catchword

Short definition from Wiktionary

Noun

1. 1
   A word under the right-hand side of the last line on a book page that repeats the first word on the following page.
2. 2
   The last word of a speech, serving as a cue for the next speaker.
3. 3
   A word or expression repeated until it becomes representative of a party, school, business, or point of view.