build a fire under (someone or something)(redirected from built a fire under him)
build a fire under (someone or something)
To motivate someone or something to take action. The deadline really built a fire under us—we never would have gotten all that work done otherwise. Something must have built a fire under Jenna—she has really started taking her schoolwork seriously.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.