Idioms and Phrases with under someone's thumb
under someone's thumb
Controlled or dominated by someone, as in He's been under his mother's thumb for years. The allusion in this metaphoric idiom is unclear, that is, why a thumb rather than a fist or some other anatomic part should symbolize control. [Mid-1700s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.