H. P. Grice: "Para-semantics and implicatura"

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.