- obvert
[obvert 词源字典]
- "Alter (a proposition) so as to infer another proposition with a contradictory predicate, e.g. ‘no men are immortal’ to ‘all men are mortal’", Early 17th century (in the sense 'turn something until it is facing'): from Latin obvertere, from ob- 'towards' + vertere 'to turn'.[obvert etymology, obvert origin, 英语词源]