Idiom meaning, usage examples, facts

1. Don’t ask Margie to make a change in our work schedule; she won’t do anything without Larry’s permission. She’s under Larry’s thumb.
2. Those two young people will never be allowed to make their own decisions or lead their own lives. Their mother will always control them. They will always be under their mother’s thumb.

Compare to: tied to (one’s) mother’s apron strings. The expression suggests a dramatic difference between the person in control and the person who is controlled, the latter being so small or so weak as to be held down by a thumb.