Confuse, upset, or bewilder, as in He tied himself into knots when he tried to explain how the engine works. This metaphoric idiom transfers a knotted tangle to mental confusion. [Late 1800s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.