digital clock vs wristwatch

digital clock

noun
  • A clock that displays the time (hours, minutes, and sometimes seconds) in digits, rather than by hands on a dial (like a analog clock). 

wristwatch

noun
  • A watch that is worn on a strap or band fastened around the wrist 

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