who's who

noun

1. a reference work containing short biographical entries on the outstanding persons in a country, industry, profession, etc.:

   a who's who in automotive engineering.

2. the outstanding or influential persons in a community, industry, profession, or other group:

   The who's who of racing will be there.

who's who

noun

1. a book or list containing the names and short biographies of famous people

Word History and Origins

Origin of who's who¹

First recorded in 1840–50

Idioms and Phrases

The outstanding or best-known individuals of a group, as in Tonight's concert features a veritable who's who of musicians . This expression comes from the name of a famous reference work, Who's Who , first published in 1849, which contains biographical sketches of famous individuals and is regularly updated. Its name in turn was based on who is who , that is, the identity of each of a number of persons, a phrase dating from the late 1300s. [Early 1900s]