insistent (adj.)youdaoicibaDictYouDict
1620s, "standing on something," from Latin insistentem (nominative insistens), present participle of insistere (see insist). Meaning "dwelling firmly on something asserted" is from 1868. Related: Insistently.
vouch (v.)youdaoicibaDictYouDict
early 14c., "summon into court to prove a title," from Anglo-French voucher, Old French vocher "to call, summon, invoke, claim," probably from Gallo-Roman *voticare, metathesis of Latin vocitare "to call to, summon insistently," frequentative of Latin vocare "to call, call upon, summon" (see voice (n.)). Meaning "guarantee to be true or accurate" is first attested 1590s. Related: Vouched; vouching.