contraposition
noun
con·tra·po·si·tion ˌkän-trə-pə-ˈzi-shən 
: the relationship between two propositions when the subject and predicate of one are respectively the negation of the predicate and the negation of the subject of the other
Word History
Etymology
Late Latin contraposition-, contrapositio, from Latin contraponere to place opposite, from contra- + ponere to place — more at position
First Known Use
1551, in the meaning defined above