c. 1400, obviacioun "encounter, contact; exposure," from Medieval Latin obviationem (nominative obviatio), noun of action from past-participle stem of obviare "act contrary to, go against" (see obviate).
1530s, "a statement contrary to common belief or expectation," from French paradoxe (14c.) and directly from Latin paradoxum "paradox, statement seemingly absurd yet really true," from Greek paradoxon "incredible statement or opinion," noun use of neuter of adjective paradoxos "contrary to expectation, incredible," from para- "contrary to" (see para- (1)) + doxa "opinion," from dokein "to appear, seem, think" (from PIE root *dek- "to take, accept").
Originally with notions of "absurd, fantastic." Meaning "statement that is seemingly self-contradictory yet not illogical or obviously untrue" is from 1560s. Specifically in logic, "a statement or proposition from an acceptable premise and following sound reasoning that yet leads to an illogical conclusion," by 1903.
before vowels, par-, word-forming element, originally in Greek-derived words, meaning "alongside, beyond; altered; contrary; irregular, abnormal," from Greek para- from para (prep.) "beside, near; issuing from; against, contrary to," from PIE *prea, from root *per- (1) "forward," hence "toward, near; against." Cognate with Old English for- "off, away." Mostly used in scientific and technical words; not usually regarded as a naturalized formative element in English.
"anything that causes injury, anything that harms or is likely to harm; a malady or disease; conduct contrary to standards of morals or righteousness," Old English yfel (see evil (adj.)).