pugnacious: [17] Latin pugnus meant ‘fist’ (it may have been related to Greek pugmé ‘fist’, source of English pygmy). From it was derived the verb pugnāre ‘hit with the fist’, hence ‘fight’, which has given English impugn [14], repugnant [14], and, via the further derivative pugnāx ‘fond of fighting’, pugnacious. => impugn, repugnant
pugnacious (adj.)
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-, *peug- "to stick, stab, to prick" (cognates: Greek pyx "with clenched fist," pygme "fist, boxing," pyktes "boxer;" Latin pungere "to pierce, prick").