face-off vs head-to-head

face-off

noun

  • A confrontation or argument between two people or groups 

  • The start of play, when two players try to get control of the puck dropped by the referee 

head-to-head

adj

  • Direct, one-to-one. 

adv

  • Directly, one-to-one. 

  • Facing one another. 

How often have the words face-off and head-to-head occurred in a corpus of books? (source: Google Ngram Viewer )