[tweak] vb [prob. alter. of ME twikken to pull sharply, fr. OE twiccian to pluck--more at twitch] vt (1601) 1: to pinch and pull with a sudden jerk and twist: twitch "~ed a bud from the stem"
2: to pinch (a person or a body part) lightly or playfully "~ed the baby's ear affectionately"
3: to make small adjustments in or to "~ the controls"; esp: fine-tune ~ vi: pull 1a, pluck
[2]tweak n (1609): an act of tweaking: pinch