The story
- Proto-Indo-European*men-
- Proto-Hellenic*mónwos
- Ancient Greekμόνος (mónos)
- Ancient Greekμονο- (mono-)
- Englishmono-
- Englishrotor
- English todaymonorotor
From mono- + rotor. Late 19th to early 20th century, originally with reference to pumps.
Etymology from Wiktionary, CC BY-SA 4.0.