sigmoid vs turned

sigmoid

adj
  • Relating to the sigmoid colon. 

  • Exhibiting logistic growth; having a graph that accelerates until it reaches a carrying capacity. 

  • Curved in two directions, like the letter "S", or the Greek ς (sigma); having a serpentine shape. 

turned

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