oppugn v.

word-forming element meaning "toward; against; before; near; across; down," also used as an intensive, from Latin ob (prep.) "in the direction of, in front of, before; toward, to, at, upon, about; in the way of; with regard to, because of," from PIE root *epi, also *opi "near, against" (see epi-).

"disposed to fight, quarrelsome," 1640s, a back-formation from pugnacity or else from Latin pugnacis, genitive of pugnax "combative, fond of fighting," from pugnare "to fight," especially with the fists, "contend against," from pugnus "a fist" (from PIE *pung-, nasalized form of root *peuk- "to prick"). Related: Pugnaciously; pugnaciousness.

also *peug-, Proto-Indo-European root meaning "to prick."

It forms all or part of: appoint; appointment; bung; compunction; contrapuntal; expugn; expunge; impugn; interpunction; oppugn; pink; poignant; point; pointe; pointillism; poniard; pounce; pugilism; pugilist; pugnacious; pugnacity; punch (n.1) "pointed tool for making holes or embossing;" punch (n.3) "a quick blow with the fist;" punch (v.) "to hit with the fist;" puncheon (n.2) "pointed tool for punching or piercing;" punctilio; punctilious; punctual; punctuate; punctuation; puncture; pungent; punty; Pygmy; repugn; repugnance; repugnant.

It is the hypothetical source of/evidence for its existence is provided by: Greek pyx "with clenched fist," pygme "fist, boxing," pyktes "boxer;" Latin pugnare "to fight," especially with the fists, pungere "to pierce, prick."