An Etymological Dictionary of the German Language/Flegel
Flegel, m. (Suab. Pflegel), ‘flail, churl,’ from MidHG. vlęgel, OHG. flęgil, m., ‘flail’; comp. Du. vlegel, E. flail; probably from MidLat. flagellum, ‘quo frumentum teritur’ (whence also Fr. fleau, ‘flail’). On account of its meaning it cannot be connected with the Teut. root flah, ‘to flay’ (OIc. flá, ‘to flay’). Yet it may be primit. allied to Lith. plakù, plàkti, ‘to strike,’ Lat. plango, Gr. πλήγνυμι, ‘to strike.’