piece of one's mind - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Frank and severe criticism, censure, as in Chuck was furious and gave him a piece of his mind. The word piece here is used in the sense of “portion,” but the portion of the mind alluded to always has a negative opinion. [Second half of 1500s]