What is a boomer?
A boomer is (was) any transient RR worker. At one time, there were more jobs than skilled railroaders, especially in times of “boom”ing traffic (wheat harvest, etc) or a local boom, say due to a mine opening. Some men travelled, habitually, from road to road. They were a figure of some romance, and figured popularly in RR fiction. One could have boomer operators, boomer conductors, boomer anythings.