Who's Who Meaning

(uncountable, idiomatic) The identities of specific people, understood in terms of such distinguishing characteristics as their backgrounds, prominence, achievements, jobs, etc., as a basis for comparing them and especially as a basis for ranking them within a social group.

Example: 1914, The Everyman Encyclopædia:
  Nearly every country has now a Who's Who, which gives a brief outline of the life and work of living men who have distinguished themselves in various ways.
1954 Nov. 22, "Education: Something for Cleo," Time:
  In the growing who's who of Negro educators, the name of Cleo W. Blackburn, 45, ranks high.
2002 April 6, "THE 1992 CAMPAIGN: Delegates; How New York Voters Determine Who Fills Seats at Democratic Convention" [1], New York Times:
  Mr. Clinton's candidates, a veritable who's who of New York Democrats, include Carol Bellamy, the former City Council president; Sandra Feldman, head of the United Federation of Teachers in New York City, and Representative Gary L. Ackerman of Queens.
2010 Feb. 11, "Dealer to the who's who of Australian art"[2], Sydney Morning Herald:
  With glittering names from a who's who of Australian art on her walls she would laugh: "Not just glittering names, glittering examples of their work, too."
1942, Milwaukee Journal:
  Sixty-one From Wisconsin Make Debut as Who's Whos [headline]:
1814, Maria Edgeworth, Patronage, ch. 23:
  Mrs. Falconer cannot well avoid asking you to some of her entertainments, and it will be pleasant to you to know who's who beforehand.
1902, Henry James, The Wings of the Dove, ch. 20:
  "Milly, it's true," she said, to be exact, "has no natural sense of social values, doesn't in the least understand our differences or know who's who or what's what."
1902, W. W. Jacobs, At Sunwich Port, ch. 5:
  "I'll learn 'im to insult a respectable British tradesman. I'll show him who's who."
1937 Sep. 27, "Fiction: Recent Books," Time:
  Readers will conjure up many a conjecture over who's who in this literary gallery.