catchword

noun

1. (historical)A word under the right-hand side of the last line on a book page that repeats the first word from the following page. Such words served as aids to the bookbinder (to check rapidly for correct placement of leaves) and were also viewed by some readers as aids to smooth reading.

   “Near-synonym: custos”

2. The last word of a speech, serving as a cue for the next speaker.
3. A word or expression repeated until it becomes representative of a party, school, business, or point of view.

   “One could give a long list of such intellectual fashions and catchwords which in the course of two or three generations have in turn dominated the thinking of the intellectual.”

   “The war itself has several names, including "the famine war" (ḥarb al-majā'a) and seferberlik, a Turkish word, meaning "travel by land," that began its wartime career as a reference to "military conscription" but quickly became a catchword for all the calamities and suffering experienced by civilians.”