Disturb
Middle English: from Old French destourber, from Latin disturbare, from dis- ‘utterly’ + turbare ‘disturb’ (from turba ‘tumult’).
wiktionary
From Middle English destourben, from Anglo-Norman distourber and Old French destorber, from Latin disturbare, intensifying for turbare(“to throw into disorder”), ultimately from Proto-Indo-European *(s)twerH-, *(s)turH-(“to rotate, swirl, twirl, move around”).
etymonline
disturb (v.)
late 13c. distourben, "to frighten, alarm, break up the tranquility of;" c. 1300, "to stop or hinder;" from Old French destorber (Old North French distourber) and directly from Latin disturbare "throw into disorder," from dis- "completely" (see dis-) + turbare "to disorder, disturb," from turba "turmoil" (see turbid). Related: Disturbed; disturbing; disturbingly.
Middle English also had the verb as distourblen, from Old French destorbler; hence also distourbler (n.) "one who disturbs or incites" (late 14c.).
