ar vs yus

ar

noun
  • The name of the Latin-script letter R/r. 

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 ar and yus occurred in a corpus of books? (source: Google Ngram Viewer )