put one's foot down (about someone or something)
Fig. to assert something strongly. The boss put her foot down and refused to accept any more changes to the plan.
put one's foot down
Take a firm stand, as in She put her foot down and said we could not go to the carnival. This idiom alludes to setting down one's foot firmly, representing a firm position. [Late 1800s]
put (one's) foot down
To take a firm stand.
put one's foot down, to
To take a firm position. The analogy presumably is to setting one or both feet in a fixed position, representing a firm stand. Although versions of this term (usually with set one’s foot down) exist from the sixteenth century on, it became current only in the nineteenth century. The OED cites James Payn’s The Luck of the Darrells (1886): “She put her foot down . . . upon the least symptoms of an unpleasantry.”