Deceive or hoodwink someone, as in His partner had pulled the wool over his eyes for years by keeping the best accounts for himself. This term alludes to the former custom of wearing a wig, which when slipping down can blind someone temporarily. [c. 1800]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.