above-board vs serious

above-board

adv
  • Honestly; openly. 

adj
  • In open sight; without trick, concealment, or deception. 

serious

adv
  • In a serious manner; seriously. 

adj
  • Committed. 

  • Without humor or expression of happiness; grave in manner or disposition 

  • Really intending what is said (or planned, etc); in earnest; not jocular or deceiving 

  • Important; weighty; not insignificant 

How often have the words above-board and serious occurred in a corpus of books? (source: Google Ngram Viewer )