Not quite a full and proper explanation as it is predicated upon front wheel lift.
Tank slapper is slang for Wobble, as compared to Weave. Head shake is a manifestation of Wobble. You can easily get headshake without the front wheel ever leaving the ground. A good example is late turn head shake due to too much rear end squat. There's not enough weight left on the front wheel for it to track properly. The front wheel never leaves the pavement, but you can still get a good head shake. First hand experience speaking. Rear wheel misalignment and too much luggage mounted high and out back can also set up a viscious wobble. Like on my 72 Norton with clubman bars, hands crushed between the bars and tank, and a huge pant load as I saw life ending in the centre lane between two big trucks. THAT was the scariest moment of my life, even to this day !
Funny thing about Sluts, it always seemed that the fellows that called a gal a slut during the daytime were always calling them on the phone for a date on Friday night.
I always enjoyed the sluts I knew, each and every one, that term told me that I wasn't gonna waste my dough on dinner and a movie just to drop her off and head home ALONE!