hácek (1997) vs inverted circumflex

hácek (1997)

inverted circumflex

noun

  • A dipping tone. 

  • Any diacritic obtained by rotating a circumflex (ˆ) 180°. 

  • A háček. 

How often have the words hácek (1997) and inverted circumflex occurred in a corpus of books? (source: Google Ngram Viewer )