alter ego vs cohort

alter ego

noun
  • Somebody's alternate personality or persona; another self. 

  • A very close and intimate friend. 

  • A corporation used by a person to conduct personal business in an attempt to shield himself or herself from personal liability, and which a court may penetrate by "piercing the corporate veil" to impose liability on the person when they commit fraud or injustice. 

cohort

noun
  • An accomplice; abettor; associate. 

  • A demographic grouping of people, especially those in a defined age group, or having a common characteristic. 

  • Any division of a Roman legion, normally of about 500 or 600 men (equalling about six centuries). 

  • Any band or body of warriors. 

  • A group of people supporting the same thing or person. 

  • A set of individuals in a program, especially when compared to previous sets of individuals within the same program. 

  • A natural group of orders of organisms, less comprehensive than a class. 

  • A colleague. 

verb
  • To associate with such a group 

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