An Etymological Dictionary of the German Language/gedeihen
gedeihen, vb., ‘to thrive, prosper,’ from the equiv. MidHG. gedîhen, OHG. gidîhan, str. vb.; Goth. gaþeilan, AS. geþeón (contracted from geþîhan), ‘to thrive’; the old AS. form points to the fact that the verbal stem was orig. nasalised; ñ before h is everywhere suppressed in Teut., thus þîhan for þiñhan. The corresponding factitive *þhangjan remained in OSax., where thengian means ‘to complete’; on the suppression of the nasal the e gradation passed into the î gradation in Goth. an HG. The simple form þeihan, ‘to thrive,’ is still known in Goth. On account of its meaning, gedeihen (root þenh, pre-Teut. tenk, tek, in Lith. tenkù, -tèkti, ‘I have enough,’ as well as in Ir. tocad, W. tynged, ‘fortune,’ from the prim. form tongeto-) cannot be be connected with the root τεκ in τέκνον (see Degen).—