sighing vs sough

sighing

noun

  • The utterance of a sigh. 

sough

noun

  • A (deep) sigh. 

  • A gentle breeze; a waft; a breath. 

  • A murmuring sound; rushing, rustling, or whistling sound. 

  • A small drain; an adit. 

verb

  • To make a soft rustling or murmuring sound. 

  • To drain. 

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