How Well Do You Know English Slang?
"pinch, pluck, twist," usually to the nose, probably 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. The noun in this sense is recorded by 1989.
Odd; crazy; flaky: Julie is tweaked; first she says she loves Doug and then she fully grovels with Bill/ ''Twin Peaks'' without the dwarves, the demons, and the tweaky humor (1980s+)
[perhaps a memory of the days when a crystal was tweaked with a ''cat's whisker'' in order to tune a primitive radio receiver]