The story
PIE word *upó From sub- (prefix meaning ‘beneath, under; secondary, subsidiary’) + imperialism.
First known use, by meaning
- from 20th c. A form of imperialism (“policy of forcefully extending a nation's authority by territorial gain or by the establishment of economic and political dominance over other nations”) which is subordinate to another imperialist power.
Etymology from Wiktionary, CC BY-SA 4.0.