The story
- Russian · calque ofмни́мая геометрия
- English todayimaginary geometry
Calque of Russian мни́мая геометрия (mnímaja geometrija), coined by mathematician Nicolai Lobachevsky, probably influenced by мни́мое чи́сло (mnímoje číslo, “imaginary number”), although his precise reasoning is unknown.
Etymology from Wiktionary, CC BY-SA 4.0.