check off vs checkmark

check off

verb
  • To mark items on a list (with a checkmark or by crossing them out) that have been chosen for keeping or removal or that have been dealt with (for example, completed or verified as correct or satisfactory); to tick off (UK), tick (UK), cross off, strike off. 

  • To carry out a decision recorded through the process of checking off an item on a list, including dealing with it, removing it from the possible choices, or removing the not checked items from further consideration. 

  • To deduct union members' dues from their wages. 

checkmark

verb
  • To mark with a ✓ symbol; to tick. 

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