tweak (v.) Look up tweak at Dictionary.com
"pinch, pluck, twist," usually to the nose, c.1600, probably from Middle English twikken "to draw, tug, pluck" (mid-15c.), from Old English twiccian "to pluck," of obscure origin; perhaps related to twitch. Meaning "to make fine adjustments" is attested from 1966. Related: Tweaked; tweaking.
tweak (n.) Look up tweak at Dictionary.com
c.1600, "a twitch, a pluck," from tweak (v.). As "a fine adjustment" by 1989.