early 15c., from Old French pacte "agreement, treaty, compact" (14c.), from Latin pactum "agreement, contract, covenant," noun use of neuter past participle of pacisci "to covenant, to agree, make a treaty," from PIE root *pag- "fix, join together, unite, make firm" (cognates: Sanskrit pasa- "cord, rope," Avestan pas- "to fetter," Greek pegnynai "to fix, make firm, fast or solid," Latin pangere "to fix, to fasten," Slavonic paž "wooden partition," Old English fegan "to join," fon "to catch seize").