nayword

noun2

1. •
   (no longer used) A watchword or catchphrase.

   • Ay, forsooth; I have spoke with her and we have a nay-word how to know one another: I come to her in white, and cry 'mum;' she cries 'budget;' and by that we know one another. — 1597
2. •
   (no longer used) A byword or proverb.