wouldn't dream of

Also, not dream of. Not occur to one, not consider, as in Even if it were lying open on my desk, I wouldn't dream of reading another person's letter. This expression uses dream of in the sense of “remotely think of.” [First half of 1500s]

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.