get one's wires crossed

Also, have one's wires crossed. Become or be confused or mistaken about something, as in If you think there's a meeting today, you really have your wires crossed; it's not till next month. This expression transfers a wrongly wired telephone or telegraph connection to human misunderstanding. [Colloquial; early 1900s]

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