habitual vs unknown

habitual

noun
  • One who does something habitually, such as a serial criminal offender. 

  • A construction representing something done habitually. 

adj
  • Pertaining to an action performed customarily, ordinarily, or usually. 

  • Of a person or thing: engaging in some behaviour as a habit or regularly. 

  • Of or relating to a habit; established as a habit; performed over and over again; recurrent, recurring. 

  • Regular or usual. 

unknown

adj
  • Not known; unidentified; not well known. 

noun
  • A variable (usually x, y or z) whose value is to be found. 

  • A person of no identity; a nonentity 

  • Any thing, place, or situation about which nothing is known; an unknown fact or piece of information. 

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