head-scratching vs helter-skelter

head-scratching

noun

  • Confusion. 

adj

  • Confusing, perplexing, puzzling. 

helter-skelter

noun

  • Confusion or turmoil. 

  • A helical fairground slide. 

adv

  • In confused, disorderly haste. 

adj

  • Carelessly hurried and confused. 

How often have the words head-scratching and helter-skelter occurred in a corpus of books? (source: Google Ngram Viewer )