A fun look at the meaning of "einlegen" and "reinlegen" what mixed pickles have to do with shoe inlays and falling for a prank.
The core idea of the root (according to English sources) was:
German sources have the meaning for focused on motion and describe it as
twitching with the foot, unrest
In German, it shifted toward a sense of tracking (by foot) and then kept going toward the sense of perceiving.
English doesn’t have many relatives – spur, spoor, spurn.
They haven’t shifted their meaning as much, so they’re still somewhat close to ankle or to a broad sense of twitching.