light a fire under

(redirected from build a fire under)

light a fire under

Also, build a fire under. Urge or goad to action, as in If we don't light a fire under that committee, they'll never do any work. This hyperbolic colloquialism uses light in the sense of "ignite," a usage dating from the mid-1100s.
See also: fire, light

light a fire under

To urge or move to action.
See also: fire, light