Greek pteron ‘wing’ + Cactus. For the “perfectly and broadly winged seed”, which Schumann considered one of the defining features of the genus. Not for the “leaf-like, two to three winged stem segments” (Genaust, Etymologisches Wörterbuch der botanischen Pflanzennamen. 3. Auflage. 1996); Schumann described the stems as “club-shaped”.
Schramm (Monatsschr. Kakteenk. 27: 159. 1917): “The Pterocactus got its name from the winged seeds, because πτερόν (pterón) means wing. So in German one can very well call the Pterocactus “wing cactus” [Flügelkaktus], although it would probably be more correct to say “wing seed cactus” [Flügelsamenkaktus].”
“Botanical Latin is essentially a written language, but the scientific names of plants often occur in speech. How they are pronounced really matters little provided they sound pleasant and are understood by all concerned.”
Maarten H.J. van der Meer (2023 Jul 14). Pterocactus. Dictionary of Cactus Names. Retrieved from https://www.cactusnames.org/pterocactus