random vs unknown quantity

random

noun
  • An undefined, unknown or unimportant person; a person of no consequence. 

  • The direction of a rake-vein. 

  • A roving motion; course without definite direction; lack of rule or method; chance. 

  • A frame for composing type. 

adj
  • Pseudorandom; mimicking the result of random selection. 

  • Apropos of nothing; lacking context; unexpected; having apparent lack of plan, cause, or reason. 

  • Characterized by or often saying random things; habitually using non sequiturs. 

  • Being out of the ordinary; unusual or unexpected. 

  • Having unpredictable outcomes and, in the ideal case, all outcomes equally probable; resulting from such selection; lacking statistical correlation. 

  • Of or relating to probability distribution. 

  • Representative and undistinguished; typical and average; selected for no particular reason. 

unknown quantity

noun
  • A person or thing whose nature or value is a mystery. 

  • Used other than figuratively or idiomatically: see unknown, quantity. 

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