1580s, in rhetoric, "professed doubt as to where to begin," from Latin, from Greek aporia "difficulty, perplexity, want of means, poverty," abstract noun from aporos "impassable, impracticable, very difficult; hard to deal with; at a loss," from a- "not, without" (see a- (3)) + poros "passage" (from PIE root *per- (2) "to lead, pass over"). Meaning "equality of reasons for or against" is by 1893.
