subreption n.

mid-15c., from Latin surrepticius "stolen, furtive, clandestine," from surreptus, past participle of surripere "seize secretly, take away, steal, plagiarize," from assimilated form of sub "from under" (hence, "secretly;" see sub-) + rapere "to snatch" (see rapid). Related: Surreptitiously.

"the obtaining or trying to obtain something by craft or deception," 1610s, from Latin obreptionem (nominative obreptio)  "a creeping or stealing on," noun of action from past-participle stem of obrepere "to creep on, creep up to," from ob "on, to" (see ob-) + repere "to creep" (see reptile). Opposed to subreption, which is to obtain something by suppression of the truth. Related: Obreptious.