hatcheck (1981) vs inverted circumflex

hatcheck (1981)

inverted circumflex

noun

  • A dipping tone. 

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

  • A háček. 

How often have the words hatcheck (1981) and inverted circumflex occurred in a corpus of books? (source: Google Ngram Viewer )