words fail me - 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.
I can't put my thoughts or feelings into words, especially because of surprise or shock, as in When she showed up at the wedding with all three ex-husbands—well, words fail me. [Second half of 1900s]