Fire under - Idioms by The Free Dictionary
*fire under someone
Fig. something that makes someone start doing something. (*Typically: build ~; light ~; start ~.) The teacher built a fire under the students, and they really started working. You had better light a fire under your staff. Either that or we will lay off some of them.
References in classic literature
It seems that each green warrior has certain objective points for his fire under
relatively identical circumstances of warfare.
Baldia factory was set on fire under
a plan, says IO
Fire fighters after the struggle of three hours were able to bring the fire under
control after that they started the cooling process with one fire tender to avoid the eruption of fire once again.