I've got to say, "tune" is such a weird word to choose, it almost sounds like a bad translation.
Tuning is associated with musical notes (originally) and then with cars (optimizing performance) and engines more generally.
It's a weird metaphor to use for an icon that's usually been called "settings".
Because settings are not tuning, because engine/car tuning isn't about choosing your preferred settings, it's about small adjustments to maximize performance.
(The visual icon makes sense since it shows the popup to toggle settings for the site.)
