What the German bird books now know as the Turmfalke has enjoyed a huge range of names over the centuries, among them Wannenweher.
A Wanne is a winnowing basket, among many other things. Since antiquity, the regular back-and-forth of winnowing has inspired what J.N. Adams delicately styles “a rustic metaphor” for other rhythmic motions, and in German, the successors of the lexicographic brothers Grimm remind us that Wanne, the instrument subjected to those motions, has been expressly glossed as denoting the feminine pelvis and associated structures. (I do not know whether the French criblette, also attested as a kestrel name, occurs with the same meaning.)
The second part of the compound, wehen, in the context of winnowing or thrashing also refers to a swaying or shaking movement. Thus, Wannenweher occupies precisely the same risqué semantic field as our English name.
This observation raises a question about the apparently innocent alternative name Rüttelfalke. The verb rütteln, meaning to sway or shake
violently, has also been used since at least the mid-nineteenth century to
refer to the hovering flight of kestrels, kites, and ospreys. That word, too,
however—and no surprise here—has been used with coarse physical signification.
The DWB declines to take a stand, noting only that “perhaps” such
raptor names as Rüttelweihe and Rüttelgeier were formed with
the more innocuous meaning of the verb in mind.