The best or choicest of anything, as in The apples from this orchard are definitely the cream of the crop. The noun cream has been used to mean “the best” since the 16th century. The French equivalent of the present term, la crème de la crème (“the cream of the cream”) was familiar in English by 1800.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.