late 14c., "to cause trouble, grief, or vexation," from Old French molester "to torment, trouble, bother" (12c.) and directly from Latin molestare "to disturb, trouble, annoy," from molestus "troublesome, annoying, unmanageable," perhaps related to moles "mass" (see mole, n.3) on notion of either "burden" or "barrier." Meaning "sexually assault" first attested 1950. Related: Molested; molesting.