'union-supportive' originates from the combination of 'union' and 'supportive', where 'union' refers to a group of workers and 'supportive' means providing encouragement or assistance.

'union' and 'supportive' have been used in English since the 19th century, and the combination 'union-supportive' emerged in the 20th century to describe a stance favoring labor unions.

Initially, it meant 'supporting a group or alliance', but over time it evolved to specifically refer to support for labor unions.