Friedrich Kluge2508246An Etymological Dictionary of the German Language, F — Flanke1891John Francis Davis
Flanke, f., ‘flank, side,’ simply ModHG., from Fr. flanc, which, with its Rom. cognate (Ital. fianco), is derived from OHG. hlanca, ‘side’ (see lenken). For Fr. fl, from Teut. hl, see flau.