insistent (adj.)

1620s, "standing on something," from Latin insistentem (nominative insistens), present participle of insistere "stand on," also "urge, insist," from in- "upon" (from PIE root *en "in") + sistere "take a stand" (see assist (v.)). Meaning "persistent, urgent, demanding attention" is from 1868. Related: Insistently.