late 14c., molesten, "to cause trouble, grief, or vexation, disturb, harass," from Old French molester "to torment, trouble, bother" (12c.) and directly from Latin molestare "to disturb, trouble, annoy," from molestus "troublesome, annoying, unmanageable," which is perhaps related to moles "mass" (see mole (n.3)) on notion of either "burden" or "barrier." Meaning "sexually assault" is attested by 1950. Related: Molested; molesting.
c. 1400, molestacioun, "action of annoying or vexing," from Old French molestacion "vexation, harassing," and directly from Medieval Latin molestationem (nominative molestatio), noun of action from past participle stem of molestare (see molest). In Scottish law it meant "the harassing of a person in his possession or occupation of lands;" in English common law it came to mean "injury inflicted upon another."
late 13c., anoien, annuien, "to harm, hurt, injure; be troublesome or vexatious to, disquiet, upset," from Anglo-French anuier, Old French enoiier "to weary, vex, anger," anuier "be troublesome or irksome to;" according to French sources these are from Late Latin inodiare "make loathsome," from Latin (esse) in odio "(it is to me) hateful," from ablative of odium "hatred," from PIE root *od- (2) "to hate" (see odium).
Also in Middle English as a noun, "feeling of irritation, displeasure, distaste" (c. 1200, still in Shakespeare), from Old French enoi, anoi "annoyance;" the same French word was borrowed into English later in a different sense as ennui. And compare Spanish enojo "offense, injury, anger;" enojar "to molest, trouble, vex." Middle English also had annoyful and annoyous (both late 14c.).