ay vs yus

ay

noun
  • The name of the Latin-script letter A. 

intj
  • All right (inter); hooray (inter); cool (inter). 

  • New Zealand spelling of eh (question tag) 

  • Ah! alas! 

yus

noun
  • Either of two letters, little yus (Ѧ) and big yus (Ѫ), representing nasal vowel sounds in the Cyrillic alphabet. The only major Slavic language retaining these sounds is Polish, which is written in the Latin alphabet. 

How often have the words ay and yus occurred in a corpus of books? (source: Google Ngram Viewer )