One who is, esp from the point of view of union members, devoted to the interests of the employer (1920+ Labor union)
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with company-man
A male worker more loyal to management than to his fellow workers; also, one who informs on fellow employees. For example, He'll never join in a strike; he's a company man. Dating from the 1920s, a period of considerable labor unrest, this term uses company in the sense of “a business concern” and was often applied as a criticism by supporters of labor unions.